From d11e8cb40a11415ac82888033977d23d52b3c8b5 Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Tue, 7 Jul 2020 13:30:42 +0400
Subject: [PATCH 01/38] added skip_list.cpp

---
 data_structures/skip_list.cpp | 185 ++++++++++++++++++++++++++++++++++
 1 file changed, 185 insertions(+)
 create mode 100644 data_structures/skip_list.cpp

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
new file mode 100644
index 000000000..8b6ec1f70
--- /dev/null
+++ b/data_structures/skip_list.cpp
@@ -0,0 +1,185 @@
+/**
+ * A skip list is a data structure that is used for storing a sorted list of items with a
+ *  help of hierarchy of linked lists that connect increasingly sparse subsequences of the items
+ * 
+ *  References used: GeeksForGeeks, https://iq.opengenus.org/skip-list/ Pseudo Code, https://ideone.com/XnXIFl from CodeForces.
+*/
+
+#include <iostream>
+#include <vector>
+#include <stdio.h>
+#include <string.h>
+using namespace std; 
+
+#define MAXLVL 2
+#define P 0.5
+  
+
+/**
+ *  Node structure [Key][Node*, Node*...]
+*/
+class Node { 
+public: 
+    int key; 
+    void* value;
+    /*Forward Array*/
+    vector<Node*> forward;
+    Node(int key, int level, void* value); 
+};
+
+  
+Node::Node(int key, int level, void* value) { 
+    this->key = key; 
+  
+    /*Initialization of forward vector*/
+    for (int i = 0; i < sizeof(Node*)*(level+1); i++){
+        forward.push_back(NULL);
+    }
+}; 
+  
+// Class for Skip list 
+class SkipList { 
+    int level; 
+    Node *header; 
+public: 
+    SkipList(); 
+    int randomLevel(); 
+    void insertElement(int, void*); 
+    void deleteElement(int); 
+    void* searchElement(int); 
+    void displayList(); 
+}; 
+  
+SkipList::SkipList() { 
+    level = 0; 
+    /* Header initialization*/
+    header = new Node(-1, MAXLVL, NULL); 
+}; 
+
+  
+/**
+ * Returns random level for skip list;
+*/
+int SkipList::randomLevel() { 
+    int lvl = 0; 
+    while(rand()%2 < P && lvl < MAXLVL) lvl++;  
+    return lvl; 
+}; 
+  
+  
+// Insert given key in skip list 
+void SkipList::insertElement(int key, void* value) { 
+    printf("Inserting %d key ... ", key);
+    Node *x = header; 
+    Node *update[MAXLVL+1]; 
+    memset(update, 0, sizeof(Node*)*(MAXLVL+1)); 
+
+
+    for(int i = level; i >= 0; i--) { 
+        while(x->forward[i] != NULL && x->forward[i]->key < key)  x = x->forward[i]; 
+        update[i] = x; 
+    } 
+
+    x = x->forward[0]; 
+
+    bool doesnt_exist = (x == NULL || x->key != key);
+    if (doesnt_exist) { 
+        int rlevel = randomLevel(); 
+  
+        if(rlevel > level) { 
+            for(int i=level+1;i<rlevel+1;i++) update[i] = header; 
+
+            /*Update current level*/
+            level = rlevel; 
+        } 
+  
+        Node* n = new Node(key, rlevel, value);
+        for(int i=0;i<=rlevel;i++) { 
+            n->forward[i] = update[i]->forward[i]; 
+            update[i]->forward[i] = n; 
+        } 
+        printf(" Inserted\n");
+    } else {
+        printf("Exists\n");
+    }
+}; 
+  
+// Delete element from skip list 
+void SkipList::deleteElement(int key) 
+{ 
+    Node *x = header; 
+  
+    Node *update[MAXLVL+1]; 
+    memset(update, 0, sizeof(Node*)*(MAXLVL+1)); 
+  
+    for(int i = level; i >= 0; i--)  { 
+        while(x->forward[i] != NULL  &&  x->forward[i]->key < key)  x = x->forward[i]; 
+        update[i] = x; 
+    } 
+  
+    x = x->forward[0]; 
+  
+    bool doesnt_exist = (x == NULL || x->key != key);
+
+    if(!doesnt_exist) { 
+        for(int i=0;i<=level;i++) {
+            if(update[i]->forward[i] != x)  break; 
+            update[i]->forward[i] = x->forward[i]; 
+        }
+       /*Remove empty levels*/
+        while(level>0 &&  header->forward[level] == 0) level--; 
+        printf("Deleted\n");
+    } else {
+        printf("Doesnt Exists\n");
+    }
+}; 
+  
+
+/**
+ * Searching element in skip list structure
+*/
+void* SkipList::searchElement(int key) { 
+    Node *x = header; 
+    printf("Searching for %d\n", key);
+
+    for(int i = level; i >= 0; i--) { 
+        while(x->forward[i] && x->forward[i]->key < key)  x = x->forward[i]; 
+    } 
+  
+    x = x->forward[0]; 
+    if(x && x->key == key){
+        printf("FOUND\n");
+        return x->value;
+    } else {
+        printf("NOT FOUND\n");
+        return NULL;
+    }
+}; 
+  
+// Display skip list level wise 
+void SkipList::displayList() { 
+    printf("----SKIP LIST STRUCTURE----\n");
+    for(int i=0; i <= level; i++) { 
+        Node *node = header->forward[i]; 
+        printf("Level %d: ", i);
+        while(node != NULL) { 
+            printf("%d ", node->key);
+            node = node->forward[i]; 
+        } 
+        printf("\n");
+    } 
+}; 
+  
+int main() 
+{ 
+    srand((unsigned)time(0)); 
+  
+    SkipList lst;
+
+    for (int j = 0; j < (1 << (MAXLVL+1)); j++){
+         int k = (rand() % (1 << (MAXLVL+1)  + 1));
+         lst.insertElement(k, &j); 
+    }
+
+    lst.displayList();
+} 
\ No newline at end of file

From ec04afc54fccb6ff4c2f5fe32833e0116ac174b3 Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Tue, 7 Jul 2020 13:34:13 +0400
Subject: [PATCH 02/38] added skip-list

---
 data_structures/skip_list.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 8b6ec1f70..31e6d06f4 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -2,7 +2,7 @@
  * A skip list is a data structure that is used for storing a sorted list of items with a
  *  help of hierarchy of linked lists that connect increasingly sparse subsequences of the items
  * 
- *  References used: GeeksForGeeks, https://iq.opengenus.org/skip-list/ Pseudo Code, https://ideone.com/XnXIFl from CodeForces.
+ *  References used: GeeksForGeeks skip list code, https://iq.opengenus.org/skip-list/ Pseudo Code.
 */
 
 #include <iostream>
@@ -104,7 +104,7 @@ void SkipList::insertElement(int key, void* value) {
     }
 }; 
   
-// Delete element from skip list 
+
 void SkipList::deleteElement(int key) 
 { 
     Node *x = header; 

From 94338f527bcd26191ed9136722cb7fba985c4233 Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Tue, 7 Jul 2020 13:43:27 +0400
Subject: [PATCH 03/38] skip_list

---
 data_structures/skip_list.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 31e6d06f4..603d1f2c3 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -9,10 +9,12 @@
 #include <vector>
 #include <stdio.h>
 #include <string.h>
-using namespace std; 
 
 #define MAXLVL 2
 #define P 0.5
+
+using std::endl;
+using std::vector;
   
 
 /**

From 2c6b8c3bf74d2875def9d296e8bac7adcf45ecbe Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Tue, 7 Jul 2020 13:46:52 +0400
Subject: [PATCH 04/38] skip_list

---
 data_structures/skip_list.cpp | 24 +++++++++++-------------
 1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 603d1f2c3..bae1a7bbe 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -27,7 +27,7 @@ public:
     /*Forward Array*/
     vector<Node*> forward;
     Node(int key, int level, void* value); 
-};
+}
 
   
 Node::Node(int key, int level, void* value) { 
@@ -37,7 +37,7 @@ Node::Node(int key, int level, void* value) {
     for (int i = 0; i < sizeof(Node*)*(level+1); i++){
         forward.push_back(NULL);
     }
-}; 
+}
   
 // Class for Skip list 
 class SkipList { 
@@ -50,14 +50,13 @@ public:
     void deleteElement(int); 
     void* searchElement(int); 
     void displayList(); 
-}; 
+}
   
 SkipList::SkipList() { 
     level = 0; 
     /* Header initialization*/
     header = new Node(-1, MAXLVL, NULL); 
-}; 
-
+}
   
 /**
  * Returns random level for skip list;
@@ -66,7 +65,7 @@ int SkipList::randomLevel() {
     int lvl = 0; 
     while(rand()%2 < P && lvl < MAXLVL) lvl++;  
     return lvl; 
-}; 
+}
   
   
 // Insert given key in skip list 
@@ -104,8 +103,7 @@ void SkipList::insertElement(int key, void* value) {
     } else {
         printf("Exists\n");
     }
-}; 
-  
+}
 
 void SkipList::deleteElement(int key) 
 { 
@@ -134,7 +132,7 @@ void SkipList::deleteElement(int key)
     } else {
         printf("Doesnt Exists\n");
     }
-}; 
+}
   
 
 /**
@@ -156,7 +154,7 @@ void* SkipList::searchElement(int key) {
         printf("NOT FOUND\n");
         return NULL;
     }
-}; 
+}
   
 // Display skip list level wise 
 void SkipList::displayList() { 
@@ -170,10 +168,9 @@ void SkipList::displayList() {
         } 
         printf("\n");
     } 
-}; 
+}
   
-int main() 
-{ 
+int main() { 
     srand((unsigned)time(0)); 
   
     SkipList lst;
@@ -184,4 +181,5 @@ int main()
     }
 
     lst.displayList();
+    return 0;
 } 
\ No newline at end of file

From f13964cab2546754e08e61eda061a260473eb7e5 Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Tue, 7 Jul 2020 14:04:44 +0400
Subject: [PATCH 05/38] skip-list

---
 data_structures/skip_list.cpp | 33 ++++++++++++++++++---------------
 1 file changed, 18 insertions(+), 15 deletions(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index bae1a7bbe..19fdc6276 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -9,12 +9,12 @@
 #include <vector>
 #include <stdio.h>
 #include <string.h>
+// using namespace std; 
+using std::vector;
+using std::endl;
 
 #define MAXLVL 2
 #define P 0.5
-
-using std::endl;
-using std::vector;
   
 
 /**
@@ -27,7 +27,7 @@ public:
     /*Forward Array*/
     vector<Node*> forward;
     Node(int key, int level, void* value); 
-}
+};
 
   
 Node::Node(int key, int level, void* value) { 
@@ -37,7 +37,7 @@ Node::Node(int key, int level, void* value) {
     for (int i = 0; i < sizeof(Node*)*(level+1); i++){
         forward.push_back(NULL);
     }
-}
+}; 
   
 // Class for Skip list 
 class SkipList { 
@@ -50,13 +50,14 @@ public:
     void deleteElement(int); 
     void* searchElement(int); 
     void displayList(); 
-}
+}; 
   
 SkipList::SkipList() { 
     level = 0; 
     /* Header initialization*/
     header = new Node(-1, MAXLVL, NULL); 
-}
+}; 
+
   
 /**
  * Returns random level for skip list;
@@ -65,7 +66,7 @@ int SkipList::randomLevel() {
     int lvl = 0; 
     while(rand()%2 < P && lvl < MAXLVL) lvl++;  
     return lvl; 
-}
+}; 
   
   
 // Insert given key in skip list 
@@ -103,7 +104,8 @@ void SkipList::insertElement(int key, void* value) {
     } else {
         printf("Exists\n");
     }
-}
+}; 
+  
 
 void SkipList::deleteElement(int key) 
 { 
@@ -132,7 +134,7 @@ void SkipList::deleteElement(int key)
     } else {
         printf("Doesnt Exists\n");
     }
-}
+}; 
   
 
 /**
@@ -154,7 +156,7 @@ void* SkipList::searchElement(int key) {
         printf("NOT FOUND\n");
         return NULL;
     }
-}
+}; 
   
 // Display skip list level wise 
 void SkipList::displayList() { 
@@ -168,9 +170,10 @@ void SkipList::displayList() {
         } 
         printf("\n");
     } 
-}
+}; 
   
-int main() { 
+int main() 
+{ 
     srand((unsigned)time(0)); 
   
     SkipList lst;
@@ -181,5 +184,5 @@ int main() {
     }
 
     lst.displayList();
-    return 0;
-} 
\ No newline at end of file
+
+} 

From 2fb95a2bf3ba4dd411dd1123a412e28e4ae9560a Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Tue, 7 Jul 2020 14:29:08 +0400
Subject: [PATCH 06/38] skip_list

---
 data_structures/skip_list.cpp | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 19fdc6276..723958866 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -37,7 +37,7 @@ Node::Node(int key, int level, void* value) {
     for (int i = 0; i < sizeof(Node*)*(level+1); i++){
         forward.push_back(NULL);
     }
-}; 
+} 
   
 // Class for Skip list 
 class SkipList { 
@@ -50,13 +50,13 @@ public:
     void deleteElement(int); 
     void* searchElement(int); 
     void displayList(); 
-}; 
+};
   
 SkipList::SkipList() { 
     level = 0; 
     /* Header initialization*/
     header = new Node(-1, MAXLVL, NULL); 
-}; 
+} 
 
   
 /**
@@ -64,9 +64,10 @@ SkipList::SkipList() {
 */
 int SkipList::randomLevel() { 
     int lvl = 0; 
-    while(rand()%2 < P && lvl < MAXLVL) lvl++;  
+    thread_local unsigned int seed = time(NULL);
+    while(rand_r(&seed)%2 < P && lvl < MAXLVL) lvl++;  
     return lvl; 
-}; 
+} 
   
   
 // Insert given key in skip list 
@@ -104,7 +105,7 @@ void SkipList::insertElement(int key, void* value) {
     } else {
         printf("Exists\n");
     }
-}; 
+} 
   
 
 void SkipList::deleteElement(int key) 
@@ -134,7 +135,7 @@ void SkipList::deleteElement(int key)
     } else {
         printf("Doesnt Exists\n");
     }
-}; 
+} 
   
 
 /**
@@ -156,7 +157,7 @@ void* SkipList::searchElement(int key) {
         printf("NOT FOUND\n");
         return NULL;
     }
-}; 
+} 
   
 // Display skip list level wise 
 void SkipList::displayList() { 
@@ -170,16 +171,17 @@ void SkipList::displayList() {
         } 
         printf("\n");
     } 
-}; 
+} 
   
 int main() 
 { 
-    srand((unsigned)time(0)); 
+        thread_local unsigned int seed = time(NULL);
+
   
     SkipList lst;
 
     for (int j = 0; j < (1 << (MAXLVL+1)); j++){
-         int k = (rand() % (1 << (MAXLVL+1)  + 1));
+         int k = (rand_r(&seed) % (1 << (MAXLVL+1)  + 1));
          lst.insertElement(k, &j); 
     }
 

From 420915fa0ddff92b6be4922f540c651136f9f6a6 Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Tue, 7 Jul 2020 14:48:30 +0400
Subject: [PATCH 07/38] skip_list

---
 data_structures/skip_list.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 723958866..550a5c9d3 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -9,6 +9,8 @@
 #include <vector>
 #include <stdio.h>
 #include <string.h>
+#include <stdlib.h>
+#include <time.h>   
 // using namespace std; 
 using std::vector;
 using std::endl;
@@ -58,6 +60,8 @@ SkipList::SkipList() {
     header = new Node(-1, MAXLVL, NULL); 
 } 
 
+
+
   
 /**
  * Returns random level for skip list;
@@ -187,4 +191,6 @@ int main()
 
     lst.displayList();
 
+
+
 } 

From 910180ff214ae669eb0a9ec6a923a7d00755d746 Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Tue, 7 Jul 2020 14:54:44 +0400
Subject: [PATCH 08/38] skip_list

---
 data_structures/skip_list.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 550a5c9d3..3b4ba500f 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -11,6 +11,8 @@
 #include <string.h>
 #include <stdlib.h>
 #include <time.h>   
+#include <cstdlib>
+
 // using namespace std; 
 using std::vector;
 using std::endl;

From 8e99383dbf8f373fc7a99fd2db8187f3f88441f4 Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Tue, 7 Jul 2020 15:13:01 +0400
Subject: [PATCH 09/38] skip_list

---
 data_structures/skip_list.cpp | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 3b4ba500f..fe5820b43 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -70,8 +70,7 @@ SkipList::SkipList() {
 */
 int SkipList::randomLevel() { 
     int lvl = 0; 
-    thread_local unsigned int seed = time(NULL);
-    while(rand_r(&seed)%2 < P && lvl < MAXLVL) lvl++;  
+    while((float)rand()/RAND_MAX < P && lvl < MAXLVL) lvl++;  
     return lvl; 
 } 
   
@@ -181,13 +180,12 @@ void SkipList::displayList() {
   
 int main() 
 { 
-        thread_local unsigned int seed = time(NULL);
+    srand((unsigned)time(0)); 
 
-  
     SkipList lst;
 
     for (int j = 0; j < (1 << (MAXLVL+1)); j++){
-         int k = (rand_r(&seed) % (1 << (MAXLVL+1)  + 1));
+         int k = (rand()% (1 << (MAXLVL+1)  + 1));
          lst.insertElement(k, &j); 
     }
 

From 2fc0d5bffeaff3845fd8b3ca774b0f9f50cc2299 Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Tue, 7 Jul 2020 16:40:47 +0400
Subject: [PATCH 10/38] skip-list corrected

---
 data_structures/skip_list.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index fe5820b43..69836e13a 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -180,12 +180,12 @@ void SkipList::displayList() {
   
 int main() 
 { 
-    srand((unsigned)time(0)); 
+    std::srand(time(nullptr));
 
     SkipList lst;
 
     for (int j = 0; j < (1 << (MAXLVL+1)); j++){
-         int k = (rand()% (1 << (MAXLVL+1)  + 1));
+         int k = (std::rand()% (1 << (MAXLVL+1)  + 1));
          lst.insertElement(k, &j); 
     }
 

From ba65d559c5912861bad589e7832becdf321bc01f Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Tue, 7 Jul 2020 16:51:47 +0400
Subject: [PATCH 11/38] skip-list documentation-polish

---
 data_structures/skip_list.cpp | 29 +++++++++++++++--------------
 1 file changed, 15 insertions(+), 14 deletions(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 69836e13a..988165db3 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -70,14 +70,14 @@ SkipList::SkipList() {
 */
 int SkipList::randomLevel() { 
     int lvl = 0; 
-    while((float)rand()/RAND_MAX < P && lvl < MAXLVL) lvl++;  
+    while(static_cast<float>(rand())/RAND_MAX < P && lvl < MAXLVL) lvl++;  
     return lvl; 
 } 
   
   
 // Insert given key in skip list 
 void SkipList::insertElement(int key, void* value) { 
-    printf("Inserting %d key ... ", key);
+    std::cout << "Inserting" << key << "...";
     Node *x = header; 
     Node *update[MAXLVL+1]; 
     memset(update, 0, sizeof(Node*)*(MAXLVL+1)); 
@@ -106,13 +106,14 @@ void SkipList::insertElement(int key, void* value) {
             n->forward[i] = update[i]->forward[i]; 
             update[i]->forward[i] = n; 
         } 
-        printf(" Inserted\n");
+        std::cout << "Inserted" << endl;
+
     } else {
-        printf("Exists\n");
+        std::cout << "Exists" << endl;
     }
 } 
   
-
+  /**Delete document by key*/
 void SkipList::deleteElement(int key) 
 { 
     Node *x = header; 
@@ -136,9 +137,9 @@ void SkipList::deleteElement(int key)
         }
        /*Remove empty levels*/
         while(level>0 &&  header->forward[level] == 0) level--; 
-        printf("Deleted\n");
+        std::cout << "Deleted" << endl;
     } else {
-        printf("Doesnt Exists\n");
+        std::cout << "Doesn't exist" << endl;
     }
 } 
   
@@ -148,7 +149,7 @@ void SkipList::deleteElement(int key)
 */
 void* SkipList::searchElement(int key) { 
     Node *x = header; 
-    printf("Searching for %d\n", key);
+    std::cout << "Searching for " + key << endl;
 
     for(int i = level; i >= 0; i--) { 
         while(x->forward[i] && x->forward[i]->key < key)  x = x->forward[i]; 
@@ -156,25 +157,25 @@ void* SkipList::searchElement(int key) {
   
     x = x->forward[0]; 
     if(x && x->key == key){
-        printf("FOUND\n");
+        std::cout << "Found" << endl;
         return x->value;
     } else {
-        printf("NOT FOUND\n");
+        std::cout << "Not Found" << endl;
         return NULL;
     }
 } 
   
 // Display skip list level wise 
 void SkipList::displayList() { 
-    printf("----SKIP LIST STRUCTURE----\n");
+    std::cout << "Displaying list:\n" << endl;
     for(int i=0; i <= level; i++) { 
         Node *node = header->forward[i]; 
-        printf("Level %d: ", i);
+        std::cout << "Level " << (i) << ": ";
         while(node != NULL) { 
-            printf("%d ", node->key);
+            std::cout << node->key << " ";
             node = node->forward[i]; 
         } 
-        printf("\n");
+        std::cout << endl;
     } 
 } 
   

From 5068ddc14d093c2434edcb359fca0d3594dff86c Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Tue, 7 Jul 2020 16:55:52 +0400
Subject: [PATCH 12/38] skip-list documentation-polish

---
 data_structures/skip_list.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 988165db3..d2ba820f4 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -70,7 +70,7 @@ SkipList::SkipList() {
 */
 int SkipList::randomLevel() { 
     int lvl = 0; 
-    while(static_cast<float>(rand())/RAND_MAX < P && lvl < MAXLVL) lvl++;  
+    while(static_cast<float>(std::rand())/RAND_MAX < P && lvl < MAXLVL) lvl++;  
     return lvl; 
 } 
   

From dcdebae395ae9edbf40461b8a1cd31659ad20526 Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Tue, 7 Jul 2020 17:24:13 +0400
Subject: [PATCH 13/38] skip-list documentation-polish

---
 data_structures/skip_list.cpp | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index d2ba820f4..782486632 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -54,7 +54,10 @@ public:
     void deleteElement(int); 
     void* searchElement(int); 
     void displayList(); 
+    ~SkipList();
 };
+
+
   
 SkipList::SkipList() { 
     level = 0; 
@@ -63,6 +66,18 @@ SkipList::SkipList() {
 } 
 
 
+SkipList::~SkipList(){
+    delete header;
+    for(int i=0; i <= level; i++) { 
+        Node *node = header->forward[i]; 
+        Node* temp;
+        while(node != NULL) { 
+            temp = node;
+            node = node->forward[i];
+            delete temp;
+        } 
+    } 
+}
 
   
 /**

From f7ab869d90db9666592980e87ce3465f76de2aaf Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Tue, 7 Jul 2020 18:16:38 +0400
Subject: [PATCH 14/38] skip list update

---
 data_structures/skip_list.cpp | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 782486632..480e9dedf 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -7,25 +7,22 @@
 
 #include <iostream>
 #include <vector>
-#include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
 #include <time.h>   
-#include <cstdlib>
 
 // using namespace std; 
 using std::vector;
 using std::endl;
 
-#define MAXLVL 2
-#define P 0.5
+#define MAXLVL 2   ///< maximum level of skip list
+#define P 0.5      ///< current probability for "coin toss"
   
 
 /**
  *  Node structure [Key][Node*, Node*...]
 */
-class Node { 
-public: 
+struct Node { 
     int key; 
     void* value;
     /*Forward Array*/
@@ -38,7 +35,7 @@ Node::Node(int key, int level, void* value) {
     this->key = key; 
   
     /*Initialization of forward vector*/
-    for (int i = 0; i < sizeof(Node*)*(level+1); i++){
+    for (int i = 0; i < (level+1); i++){
         forward.push_back(NULL);
     }
 } 
@@ -67,7 +64,6 @@ SkipList::SkipList() {
 
 
 SkipList::~SkipList(){
-    delete header;
     for(int i=0; i <= level; i++) { 
         Node *node = header->forward[i]; 
         Node* temp;
@@ -77,6 +73,7 @@ SkipList::~SkipList(){
             delete temp;
         } 
     } 
+    delete header;
 }
 
   
@@ -201,12 +198,10 @@ int main()
     SkipList lst;
 
     for (int j = 0; j < (1 << (MAXLVL+1)); j++){
-         int k = (std::rand()% (1 << (MAXLVL+1)  + 1));
+         int k = (std::rand()%( 1 << (MAXLVL+2)) + 1);
          lst.insertElement(k, &j); 
     }
 
     lst.displayList();
 
-
-
 } 

From fd8affb59d86b90f244adcd3ccb49dc2b1acf09a Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Tue, 7 Jul 2020 18:20:21 +0400
Subject: [PATCH 15/38] skip_list

---
 data_structures/skip_list.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 480e9dedf..9d829349e 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -9,7 +9,7 @@
 #include <vector>
 #include <string.h>
 #include <stdlib.h>
-#include <time.h>   
+#include <ctime>   
 
 // using namespace std; 
 using std::vector;

From 4cebe7c68270e5474e1b0a3c65355157a741b23b Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Tue, 7 Jul 2020 18:21:12 +0400
Subject: [PATCH 16/38] skip_list

---
 data_structures/skip_list.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 9d829349e..180d9c32d 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -193,7 +193,7 @@ void SkipList::displayList() {
   
 int main() 
 { 
-    std::srand(time(nullptr));
+    std::srand(std::time(nullptr));
 
     SkipList lst;
 

From ac0d11977d0b8fcc3396855bed490bfc690b2ad4 Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Tue, 7 Jul 2020 19:17:37 +0400
Subject: [PATCH 17/38] skip_list

---
 data_structures/skip_list.cpp | 66 ++++++++++++++++++++++-------------
 1 file changed, 41 insertions(+), 25 deletions(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 180d9c32d..c41d3c2e1 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -2,7 +2,7 @@
  * A skip list is a data structure that is used for storing a sorted list of items with a
  *  help of hierarchy of linked lists that connect increasingly sparse subsequences of the items
  * 
- *  References used: GeeksForGeeks skip list code, https://iq.opengenus.org/skip-list/ Pseudo Code.
+ *  References used: GeeksForGeeks skip list code, https://iq.opengenus.org/skip-list/  Code and PseudoCode.
 */
 
 #include <iostream>
@@ -15,28 +15,31 @@
 using std::vector;
 using std::endl;
 
-#define MAXLVL 2   ///< maximum level of skip list
-#define P 0.5      ///< current probability for "coin toss"
+#define MAX_LEVEL 2   ///< maximum level of skip list
+#define PROBABILITY 0.5      ///< current probability for "coin toss"
   
 
 /**
  *  Node structure [Key][Node*, Node*...]
 */
 struct Node { 
-    int key; 
+    int key;
+    /* pointer of value */
     void* value;
     /*Forward Array*/
     vector<Node*> forward;
     Node(int key, int level, void* value); 
 };
 
-  
+/**
+ * Creates node with provided key, level and value;
+*/
 Node::Node(int key, int level, void* value) { 
     this->key = key; 
   
     /*Initialization of forward vector*/
     for (int i = 0; i < (level+1); i++){
-        forward.push_back(NULL);
+        forward.push_back(nullptr);
     }
 } 
   
@@ -55,11 +58,13 @@ public:
 };
 
 
-  
+/**\
+ * Skeep List constructor;
+*/
 SkipList::SkipList() { 
     level = 0; 
     /* Header initialization*/
-    header = new Node(-1, MAXLVL, NULL); 
+    header = new Node(-1, MAX_LEVEL, nullptr); 
 } 
 
 
@@ -67,7 +72,7 @@ SkipList::~SkipList(){
     for(int i=0; i <= level; i++) { 
         Node *node = header->forward[i]; 
         Node* temp;
-        while(node != NULL) { 
+        while(node != nullptr) { 
             temp = node;
             node = node->forward[i];
             delete temp;
@@ -82,27 +87,31 @@ SkipList::~SkipList(){
 */
 int SkipList::randomLevel() { 
     int lvl = 0; 
-    while(static_cast<float>(std::rand())/RAND_MAX < P && lvl < MAXLVL) lvl++;  
+    while(static_cast<float>(std::rand())/RAND_MAX < PROBABILITY && lvl < MAX_LEVEL) lvl++;  
     return lvl; 
 } 
   
   
-// Insert given key in skip list 
+  
+/**
+ * Inserts elements with given key and value;
+ * It's level is computed by randomLevel() function.
+*/
 void SkipList::insertElement(int key, void* value) { 
     std::cout << "Inserting" << key << "...";
     Node *x = header; 
-    Node *update[MAXLVL+1]; 
-    memset(update, 0, sizeof(Node*)*(MAXLVL+1)); 
+    Node *update[MAX_LEVEL+1]; 
+    memset(update, 0, sizeof(Node*)*(MAX_LEVEL+1)); 
 
 
     for(int i = level; i >= 0; i--) { 
-        while(x->forward[i] != NULL && x->forward[i]->key < key)  x = x->forward[i]; 
+        while(x->forward[i] != nullptr && x->forward[i]->key < key)  x = x->forward[i]; 
         update[i] = x; 
     } 
 
     x = x->forward[0]; 
 
-    bool doesnt_exist = (x == NULL || x->key != key);
+    bool doesnt_exist = (x == nullptr || x->key != key);
     if (doesnt_exist) { 
         int rlevel = randomLevel(); 
   
@@ -130,17 +139,17 @@ void SkipList::deleteElement(int key)
 { 
     Node *x = header; 
   
-    Node *update[MAXLVL+1]; 
-    memset(update, 0, sizeof(Node*)*(MAXLVL+1)); 
+    Node *update[MAX_LEVEL+1]; 
+    memset(update, 0, sizeof(Node*)*(MAX_LEVEL+1)); 
   
     for(int i = level; i >= 0; i--)  { 
-        while(x->forward[i] != NULL  &&  x->forward[i]->key < key)  x = x->forward[i]; 
+        while(x->forward[i] != nullptr  &&  x->forward[i]->key < key)  x = x->forward[i]; 
         update[i] = x; 
     } 
   
     x = x->forward[0]; 
   
-    bool doesnt_exist = (x == NULL || x->key != key);
+    bool doesnt_exist = (x == nullptr || x->key != key);
 
     if(!doesnt_exist) { 
         for(int i=0;i<=level;i++) {
@@ -173,32 +182,39 @@ void* SkipList::searchElement(int key) {
         return x->value;
     } else {
         std::cout << "Not Found" << endl;
-        return NULL;
+        return nullptr;
     }
 } 
   
-// Display skip list level wise 
+/**
+ * Display skip list level wise 
+ */
 void SkipList::displayList() { 
     std::cout << "Displaying list:\n" << endl;
     for(int i=0; i <= level; i++) { 
         Node *node = header->forward[i]; 
         std::cout << "Level " << (i) << ": ";
-        while(node != NULL) { 
+        while(node != nullptr) { 
             std::cout << node->key << " ";
             node = node->forward[i]; 
         } 
         std::cout << endl;
     } 
 } 
-  
+
+
+/**
+ * Main function:
+ * Creates and inserts random 2^[number of levels] elements into the skip lists and than displays it
+ */  
 int main() 
 { 
     std::srand(std::time(nullptr));
 
     SkipList lst;
 
-    for (int j = 0; j < (1 << (MAXLVL+1)); j++){
-         int k = (std::rand()%( 1 << (MAXLVL+2)) + 1);
+    for (int j = 0; j < (1 << (MAX_LEVEL+1)); j++){
+         int k = (std::rand()%( 1 << (MAX_LEVEL+2)) + 1);
          lst.insertElement(k, &j); 
     }
 

From d5b897d40e3354e64c6c1bb1bf91435a2bb769b4 Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Tue, 7 Jul 2020 19:22:32 +0400
Subject: [PATCH 18/38] improve

---
 data_structures/skip_list.cpp | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index c41d3c2e1..5881f5d27 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -7,8 +7,7 @@
 
 #include <iostream>
 #include <vector>
-#include <string.h>
-#include <stdlib.h>
+#include <cstring>
 #include <ctime>   
 
 // using namespace std; 

From ea57ad29cd350a265be297a49bc8c65c8dfcc825 Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Tue, 7 Jul 2020 19:55:47 +0400
Subject: [PATCH 19/38] improve

---
 data_structures/skip_list.cpp | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 5881f5d27..eb8e5cd87 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -23,26 +23,28 @@ using std::endl;
 */
 struct Node { 
     int key;
-    /* pointer of value */
+    //pointer of value 
     void* value;
-    /*Forward Array*/
+    //Forward Array
     vector<Node*> forward;
     Node(int key, int level, void* value); 
 };
 
 /**
- * Creates node with provided key, level and value;
+ * Creates node with provided key, level and value
 */
 Node::Node(int key, int level, void* value) { 
     this->key = key; 
   
-    /*Initialization of forward vector*/
+    //Initialization of forward vector
     for (int i = 0; i < (level+1); i++){
         forward.push_back(nullptr);
     }
 } 
   
-// Class for Skip list 
+/**
+ * SkipList class
+*/
 class SkipList { 
     int level; 
     Node *header; 
@@ -57,12 +59,12 @@ public:
 };
 
 
-/**\
- * Skeep List constructor;
+/**
+ * Skeep List constructor
 */
 SkipList::SkipList() { 
     level = 0; 
-    /* Header initialization*/
+    // Header initialization
     header = new Node(-1, MAX_LEVEL, nullptr); 
 } 
 
@@ -117,7 +119,7 @@ void SkipList::insertElement(int key, void* value) {
         if(rlevel > level) { 
             for(int i=level+1;i<rlevel+1;i++) update[i] = header; 
 
-            /*Update current level*/
+            //Update current level
             level = rlevel; 
         } 
   

From 1df1e1eabc7bab55764d1e145c3b40db7820a419 Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Tue, 7 Jul 2020 19:58:10 +0400
Subject: [PATCH 20/38] improve

---
 data_structures/skip_list.cpp | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index eb8e5cd87..25a9aae2a 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -1,4 +1,4 @@
-/**
+/*
  * A skip list is a data structure that is used for storing a sorted list of items with a
  *  help of hierarchy of linked lists that connect increasingly sparse subsequences of the items
  * 
@@ -18,7 +18,7 @@ using std::endl;
 #define PROBABILITY 0.5      ///< current probability for "coin toss"
   
 
-/**
+/*
  *  Node structure [Key][Node*, Node*...]
 */
 struct Node { 
@@ -30,7 +30,7 @@ struct Node {
     Node(int key, int level, void* value); 
 };
 
-/**
+/*
  * Creates node with provided key, level and value
 */
 Node::Node(int key, int level, void* value) { 
@@ -42,7 +42,7 @@ Node::Node(int key, int level, void* value) {
     }
 } 
   
-/**
+/*
  * SkipList class
 */
 class SkipList { 
@@ -59,7 +59,7 @@ public:
 };
 
 
-/**
+/*
  * Skeep List constructor
 */
 SkipList::SkipList() { 
@@ -83,7 +83,7 @@ SkipList::~SkipList(){
 }
 
   
-/**
+/*
  * Returns random level for skip list;
 */
 int SkipList::randomLevel() { 
@@ -94,7 +94,7 @@ int SkipList::randomLevel() {
   
   
   
-/**
+/*
  * Inserts elements with given key and value;
  * It's level is computed by randomLevel() function.
 */
@@ -135,7 +135,9 @@ void SkipList::insertElement(int key, void* value) {
     }
 } 
   
-  /**Delete document by key*/
+/*
+ * Delete document by key
+*/
 void SkipList::deleteElement(int key) 
 { 
     Node *x = header; 
@@ -166,7 +168,7 @@ void SkipList::deleteElement(int key)
 } 
   
 
-/**
+/*
  * Searching element in skip list structure
 */
 void* SkipList::searchElement(int key) { 
@@ -187,7 +189,7 @@ void* SkipList::searchElement(int key) {
     }
 } 
   
-/**
+/*
  * Display skip list level wise 
  */
 void SkipList::displayList() { 
@@ -204,7 +206,7 @@ void SkipList::displayList() {
 } 
 
 
-/**
+/*
  * Main function:
  * Creates and inserts random 2^[number of levels] elements into the skip lists and than displays it
  */  

From 662841bac7e69b6414ab09ed9871b63de7b6b65d Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Tue, 7 Jul 2020 19:59:54 +0400
Subject: [PATCH 21/38] improve

---
 data_structures/skip_list.cpp | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 25a9aae2a..729ce1d80 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -18,7 +18,7 @@ using std::endl;
 #define PROBABILITY 0.5      ///< current probability for "coin toss"
   
 
-/*
+/**
  *  Node structure [Key][Node*, Node*...]
 */
 struct Node { 
@@ -30,7 +30,7 @@ struct Node {
     Node(int key, int level, void* value); 
 };
 
-/*
+/**
  * Creates node with provided key, level and value
 */
 Node::Node(int key, int level, void* value) { 
@@ -42,7 +42,7 @@ Node::Node(int key, int level, void* value) {
     }
 } 
   
-/*
+/**
  * SkipList class
 */
 class SkipList { 
@@ -59,7 +59,7 @@ public:
 };
 
 
-/*
+/**
  * Skeep List constructor
 */
 SkipList::SkipList() { 
@@ -68,7 +68,9 @@ SkipList::SkipList() {
     header = new Node(-1, MAX_LEVEL, nullptr); 
 } 
 
-
+/**
+ * Destructor for skiplist class
+*/
 SkipList::~SkipList(){
     for(int i=0; i <= level; i++) { 
         Node *node = header->forward[i]; 
@@ -83,7 +85,7 @@ SkipList::~SkipList(){
 }
 
   
-/*
+/**
  * Returns random level for skip list;
 */
 int SkipList::randomLevel() { 
@@ -94,7 +96,7 @@ int SkipList::randomLevel() {
   
   
   
-/*
+/**
  * Inserts elements with given key and value;
  * It's level is computed by randomLevel() function.
 */
@@ -135,7 +137,7 @@ void SkipList::insertElement(int key, void* value) {
     }
 } 
   
-/*
+/**
  * Delete document by key
 */
 void SkipList::deleteElement(int key) 
@@ -168,7 +170,7 @@ void SkipList::deleteElement(int key)
 } 
   
 
-/*
+/**
  * Searching element in skip list structure
 */
 void* SkipList::searchElement(int key) { 
@@ -206,7 +208,7 @@ void SkipList::displayList() {
 } 
 
 
-/*
+/**
  * Main function:
  * Creates and inserts random 2^[number of levels] elements into the skip lists and than displays it
  */  

From 45b21f287116aaffd52fe8b40a9d5104a5ab31e7 Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Tue, 7 Jul 2020 20:29:37 +0400
Subject: [PATCH 22/38] improve

---
 data_structures/skip_list.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 729ce1d80..1fc9f3e0e 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -1,4 +1,4 @@
-/*
+/**
  * A skip list is a data structure that is used for storing a sorted list of items with a
  *  help of hierarchy of linked lists that connect increasingly sparse subsequences of the items
  * 

From 59a8b3d4a295e7af34437151e0f50c973eb7e77d Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Wed, 8 Jul 2020 20:43:52 +0400
Subject: [PATCH 23/38] Update data_structures/skip_list.cpp

Co-authored-by: David Leal <halfpacho@gmail.com>
---
 data_structures/skip_list.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 1fc9f3e0e..62ae51ea9 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -210,7 +210,8 @@ void SkipList::displayList() {
 
 /**
  * Main function:
- * Creates and inserts random 2^[number of levels] elements into the skip lists and than displays it
+ * Creates and inserts random 2^[number of levels]
+ * elements into the skip lists and than displays it
  */  
 int main() 
 { 

From a5ca794aa4e27e6fb5d9c6e591449458ee5b8fe4 Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Wed, 8 Jul 2020 20:46:50 +0400
Subject: [PATCH 24/38] sk

---
 data_structures/skip_list.cpp | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 1fc9f3e0e..b7aab7882 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -10,7 +10,6 @@
 #include <cstring>
 #include <ctime>   
 
-// using namespace std; 
 using std::vector;
 using std::endl;
 
@@ -23,9 +22,9 @@ using std::endl;
 */
 struct Node { 
     int key;
-    //pointer of value 
+    // pointer of value 
     void* value;
-    //Forward Array
+    // Forward Array
     vector<Node*> forward;
     Node(int key, int level, void* value); 
 };

From bba0db36ec5aa125fa4acdb35191e8348aaa670b Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Wed, 8 Jul 2020 20:47:43 +0400
Subject: [PATCH 25/38] sk

---
 data_structures/skip_list.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 3e13ee696..922c5a1e3 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -120,7 +120,7 @@ void SkipList::insertElement(int key, void* value) {
         if(rlevel > level) { 
             for(int i=level+1;i<rlevel+1;i++) update[i] = header; 
 
-            //Update current level
+            // Update current level
             level = rlevel; 
         } 
   
@@ -160,7 +160,7 @@ void SkipList::deleteElement(int key)
             if(update[i]->forward[i] != x)  break; 
             update[i]->forward[i] = x->forward[i]; 
         }
-       /*Remove empty levels*/
+       /* Remove empty levels*/
         while(level>0 &&  header->forward[level] == 0) level--; 
         std::cout << "Deleted" << endl;
     } else {

From ab1ddb364f3116e08bd52f6424f5cfbaca484157 Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Fri, 10 Jul 2020 20:39:33 +0400
Subject: [PATCH 26/38] documentation

---
 data_structures/skip_list.cpp | 34 ++++++++++++++++++++++++----------
 1 file changed, 24 insertions(+), 10 deletions(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 922c5a1e3..dc9b06776 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -13,8 +13,8 @@
 using std::vector;
 using std::endl;
 
-#define MAX_LEVEL 2   ///< maximum level of skip list
-#define PROBABILITY 0.5      ///< current probability for "coin toss"
+#define MAX_LEVEL 2   ///< Maximum level of skip list
+#define PROBABILITY 0.5      ///< Current probability for "coin toss"
   
 
 /**
@@ -24,13 +24,18 @@ struct Node {
     int key;
     // pointer of value 
     void* value;
-    // Forward Array
+    // Forward Array points to the neighbour (right)
+    // nodes of the given one in all levels
     vector<Node*> forward;
+    // Constructor of the node
     Node(int key, int level, void* value); 
 };
 
 /**
  * Creates node with provided key, level and value
+ * @param key is number that is used for comparision
+ * @param level is the maximum level node's going to added
+ * 
 */
 Node::Node(int key, int level, void* value) { 
     this->key = key; 
@@ -42,10 +47,12 @@ Node::Node(int key, int level, void* value) {
 } 
   
 /**
- * SkipList class
+ * SkipList class implementation with basic methods
 */
 class SkipList { 
+    // Maximum level of the skiplist
     int level; 
+    // Pointer to the header node
     Node *header; 
 public: 
     SkipList(); 
@@ -59,7 +66,8 @@ public:
 
 
 /**
- * Skeep List constructor
+ * Skeep List constructor. Initializes header, start
+ * Node for searching in the list
 */
 SkipList::SkipList() { 
     level = 0; 
@@ -85,7 +93,9 @@ SkipList::~SkipList(){
 
   
 /**
- * Returns random level for skip list;
+ * Returns random level of the skip list.
+ * Every higher level is 2 times less likely.
+ * @return lvl: random level for skip list;
 */
 int SkipList::randomLevel() { 
     int lvl = 0; 
@@ -98,6 +108,8 @@ int SkipList::randomLevel() {
 /**
  * Inserts elements with given key and value;
  * It's level is computed by randomLevel() function.
+ * @param key is number that is used for comparision
+ * @param value pointer to a value, that can be any type
 */
 void SkipList::insertElement(int key, void* value) { 
     std::cout << "Inserting" << key << "...";
@@ -137,10 +149,10 @@ void SkipList::insertElement(int key, void* value) {
 } 
   
 /**
- * Delete document by key
+ * Deletes an element by key and prints if has been removed successfully 
+ * @param key is number that is used for comparision.
 */
-void SkipList::deleteElement(int key) 
-{ 
+void SkipList::deleteElement(int key) { 
     Node *x = header; 
   
     Node *update[MAX_LEVEL+1]; 
@@ -171,6 +183,8 @@ void SkipList::deleteElement(int key)
 
 /**
  * Searching element in skip list structure
+ * @param key is number that is used for comparision
+ * @return pointer to the value of the node
 */
 void* SkipList::searchElement(int key) { 
     Node *x = header; 
@@ -191,7 +205,7 @@ void* SkipList::searchElement(int key) {
 } 
   
 /*
- * Display skip list level wise 
+ * Display skip list level
  */
 void SkipList::displayList() { 
     std::cout << "Displaying list:\n" << endl;

From d59005678d7b2f294df26c088842ab3e44f85f31 Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Fri, 10 Jul 2020 20:40:00 +0400
Subject: [PATCH 27/38] documentation

---
 data_structures/skip_list.cpp | 1 -
 1 file changed, 1 deletion(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index dc9b06776..80717050a 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -35,7 +35,6 @@ struct Node {
  * Creates node with provided key, level and value
  * @param key is number that is used for comparision
  * @param level is the maximum level node's going to added
- * 
 */
 Node::Node(int key, int level, void* value) { 
     this->key = key; 

From a90dcc5f66126049e91e0fa3835a55f6afb7d9fe Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Fri, 10 Jul 2020 21:10:21 +0400
Subject: [PATCH 28/38] parameters

---
 data_structures/skip_list.cpp | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 80717050a..37839dfdb 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -1,8 +1,12 @@
 /**
+ * @file skip_list.cpp
+ * @brief data struccture for fast searching and insertion (O(log(n)))
+ * @details
  * A skip list is a data structure that is used for storing a sorted list of items with a
- *  help of hierarchy of linked lists that connect increasingly sparse subsequences of the items
+ * help of hierarchy of linked lists that connect increasingly sparse subsequences of the items
  * 
- *  References used: GeeksForGeeks skip list code, https://iq.opengenus.org/skip-list/  Code and PseudoCode.
+ * References used: GeeksForGeeks skip list code, https://iq.opengenus.org/skip-list/  PseudoCode and Code
+ * .
 */
 
 #include <iostream>

From 2fecf67a365b9329036d623467dde998903ead98 Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Fri, 10 Jul 2020 21:11:20 +0400
Subject: [PATCH 29/38] parameters

---
 data_structures/skip_list.cpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 37839dfdb..6159506a0 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -6,6 +6,7 @@
  * help of hierarchy of linked lists that connect increasingly sparse subsequences of the items
  * 
  * References used: GeeksForGeeks skip list code, https://iq.opengenus.org/skip-list/  PseudoCode and Code
+ * @author enqidu
  * .
 */
 

From b1b3b310a403398d279cbe6c619d109068fe11e1 Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Fri, 10 Jul 2020 21:27:22 +0400
Subject: [PATCH 30/38] Update data_structures/skip_list.cpp

Co-authored-by: Krishna Vedala <7001608+kvedala@users.noreply.github.com>
---
 data_structures/skip_list.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 6159506a0..515c6d138 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -5,7 +5,7 @@
  * A skip list is a data structure that is used for storing a sorted list of items with a
  * help of hierarchy of linked lists that connect increasingly sparse subsequences of the items
  * 
- * References used: GeeksForGeeks skip list code, https://iq.opengenus.org/skip-list/  PseudoCode and Code
+ * References used: [GeeksForGeek](https://www.geeksforgeeks.org/skip-list/), [OpenGenus](https://iq.opengenus.org/skip-list) for PseudoCode and Code
  * @author enqidu
  * .
 */

From 5d225aba874d4b74021c1865f62148517a869f30 Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Fri, 10 Jul 2020 21:27:35 +0400
Subject: [PATCH 31/38] Update data_structures/skip_list.cpp

Co-authored-by: Krishna Vedala <7001608+kvedala@users.noreply.github.com>
---
 data_structures/skip_list.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 515c6d138..cefd23403 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -6,7 +6,7 @@
  * help of hierarchy of linked lists that connect increasingly sparse subsequences of the items
  * 
  * References used: [GeeksForGeek](https://www.geeksforgeeks.org/skip-list/), [OpenGenus](https://iq.opengenus.org/skip-list) for PseudoCode and Code
- * @author enqidu
+ * @author [enqidu](https://github.com/enqidu)
  * .
 */
 

From af49a02ed85b944d88c13393c0ecd2cd30f5a0d7 Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Fri, 10 Jul 2020 21:27:51 +0400
Subject: [PATCH 32/38] Update data_structures/skip_list.cpp

Co-authored-by: Krishna Vedala <7001608+kvedala@users.noreply.github.com>
---
 data_structures/skip_list.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index cefd23403..6e6d78e13 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -1,6 +1,6 @@
 /**
  * @file skip_list.cpp
- * @brief data struccture for fast searching and insertion (O(log(n)))
+ * @brief Data structure for fast searching and insertion in \f$O(\log n)\f$ time
  * @details
  * A skip list is a data structure that is used for storing a sorted list of items with a
  * help of hierarchy of linked lists that connect increasingly sparse subsequences of the items

From a707d710b58e5921d7f7131932f48f7e7860e7bd Mon Sep 17 00:00:00 2001
From: enqidu <dachikurcxalia@gmail.com>
Date: Sun, 12 Jul 2020 19:24:46 +0400
Subject: [PATCH 33/38] update

---
 data_structures/skip_list.cpp | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 6159506a0..f0a17815a 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -26,12 +26,9 @@ using std::endl;
  *  Node structure [Key][Node*, Node*...]
 */
 struct Node { 
-    int key;
-    // pointer of value 
-    void* value;
-    // Forward Array points to the neighbour (right)
-    // nodes of the given one in all levels
-    vector<Node*> forward;
+    int key; ///< key integer
+    void* value;  ///< pointer of value 
+    vector<Node*> forward;  ///< nodes of the given one in all levels
     // Constructor of the node
     Node(int key, int level, void* value); 
 };
@@ -54,10 +51,8 @@ Node::Node(int key, int level, void* value) {
  * SkipList class implementation with basic methods
 */
 class SkipList { 
-    // Maximum level of the skiplist
-    int level; 
-    // Pointer to the header node
-    Node *header; 
+    int level;  ///< Maximum level of the skiplist
+    Node *header; ///< Pointer to the header node
 public: 
     SkipList(); 
     int randomLevel(); 

From f970ce361cd1f17e289068a1e36c19eb362db1a0 Mon Sep 17 00:00:00 2001
From: Krishna Vedala <7001608+kvedala@users.noreply.github.com>
Date: Sun, 12 Jul 2020 17:00:27 -0400
Subject: [PATCH 34/38] tidied up code based on error reports by clang-tidy

---
 data_structures/skip_list.cpp | 422 +++++++++++++++++-----------------
 1 file changed, 208 insertions(+), 214 deletions(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 373b93dad..d7982f866 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -1,241 +1,235 @@
 /**
  * @file skip_list.cpp
- * @brief Data structure for fast searching and insertion in \f$O(\log n)\f$ time
+ * @brief Data structure for fast searching and insertion in \f$O(\log n)\f$
+ * time
  * @details
- * A skip list is a data structure that is used for storing a sorted list of items with a
- * help of hierarchy of linked lists that connect increasingly sparse subsequences of the items
- * 
- * References used: [GeeksForGeek](https://www.geeksforgeeks.org/skip-list/), [OpenGenus](https://iq.opengenus.org/skip-list) for PseudoCode and Code
+ * A skip list is a data structure that is used for storing a sorted list of
+ * items with a help of hierarchy of linked lists that connect increasingly
+ * sparse subsequences of the items
+ *
+ * References used: [GeeksForGeek](https://www.geeksforgeeks.org/skip-list/),
+ * [OpenGenus](https://iq.opengenus.org/skip-list) for PseudoCode and Code
  * @author [enqidu](https://github.com/enqidu)
- * .
-*/
+ * @author [Krishna Vedala](https://github.com/kvedala)
+ */
 
-#include <iostream>
-#include <vector>
+#include <array>
 #include <cstring>
-#include <ctime>   
+#include <ctime>
+#include <iostream>
+#include <memory>
+#include <vector>
 
-using std::vector;
-using std::endl;
-
-#define MAX_LEVEL 2   ///< Maximum level of skip list
-#define PROBABILITY 0.5      ///< Current probability for "coin toss"
-  
+/** \namespace data_structure
+ * \brief Data-structure algorithms
+ */
+namespace data_structure {
+constexpr int MAX_LEVEL = 2;        ///< Maximum level of skip list
+constexpr float PROBABILITY = 0.5;  ///< Current probability for "coin toss"
 
 /**
  *  Node structure [Key][Node*, Node*...]
-*/
-struct Node { 
-    int key; ///< key integer
-    void* value;  ///< pointer of value 
-    vector<Node*> forward;  ///< nodes of the given one in all levels
-    // Constructor of the node
-    Node(int key, int level, void* value); 
+ */
+struct Node {
+    int key;      ///< key integer
+    void* value;  ///< pointer of value
+    std::vector<std::shared_ptr<Node>>
+        forward;  ///< nodes of the given one in all levels
+
+    /**
+     * Creates node with provided key, level and value
+     * @param key is number that is used for comparision
+     * @param level is the maximum level node's going to added
+     */
+    Node(int key, int level, void* value = nullptr) : key(key) {
+        // Initialization of forward vector
+        for (int i = 0; i < (level + 1); i++) {
+            forward.push_back(nullptr);
+        }
+    }
 };
 
-/**
- * Creates node with provided key, level and value
- * @param key is number that is used for comparision
- * @param level is the maximum level node's going to added
-*/
-Node::Node(int key, int level, void* value) { 
-    this->key = key; 
-  
-    //Initialization of forward vector
-    for (int i = 0; i < (level+1); i++){
-        forward.push_back(nullptr);
-    }
-} 
-  
 /**
  * SkipList class implementation with basic methods
-*/
-class SkipList { 
-    int level;  ///< Maximum level of the skiplist
-    Node *header; ///< Pointer to the header node
-public: 
-    SkipList(); 
-    int randomLevel(); 
-    void insertElement(int, void*); 
-    void deleteElement(int); 
-    void* searchElement(int); 
-    void displayList(); 
-    ~SkipList();
+ */
+class SkipList {
+    int level;                     ///< Maximum level of the skiplist
+    std::shared_ptr<Node> header;  ///< Pointer to the header node
+
+ public:
+    /**
+     * Skip List constructor. Initializes header, start
+     * Node for searching in the list
+     */
+    SkipList() {
+        level = 0;
+        // Header initialization
+        header = std::shared_ptr<Node>(new Node(-1, MAX_LEVEL));
+    }
+
+    /**
+     * Destructor for skiplist class
+     */
+    ~SkipList() {
+        for (int i = 0; i <= level; i++) {
+            std::shared_ptr<Node> node = header->forward[i];
+            std::shared_ptr<Node> temp;
+            while (node != nullptr) {
+                temp = node;
+                node = node->forward[i];
+                temp.reset();
+            }
+        }
+        header.reset();
+    }
+
+    /**
+     * Returns random level of the skip list.
+     * Every higher level is 2 times less likely.
+     * @return random level for skip list
+     */
+    int randomLevel() {
+        int lvl = 0;
+        while (static_cast<float>(std::rand() / RAND_MAX) < PROBABILITY &&
+               lvl < MAX_LEVEL)
+            lvl++;
+        return lvl;
+    }
+
+    /**
+     * Inserts elements with given key and value;
+     * It's level is computed by randomLevel() function.
+     * @param key is number that is used for comparision
+     * @param value pointer to a value, that can be any type
+     */
+    void insertElement(int key, void* value) {
+        std::cout << "Inserting" << key << "...";
+        std::shared_ptr<Node> x = header;
+        std::array<std::shared_ptr<Node>, MAX_LEVEL + 1> update;
+        update.fill(nullptr);
+
+        for (int i = level; i >= 0; i--) {
+            while (x->forward[i] != nullptr && x->forward[i]->key < key)
+                x = x->forward[i];
+            update[i] = x;
+        }
+
+        x = x->forward[0];
+
+        bool doesnt_exist = (x == nullptr || x->key != key);
+        if (doesnt_exist) {
+            int rlevel = randomLevel();
+
+            if (rlevel > level) {
+                for (int i = level + 1; i < rlevel + 1; i++) update[i] = header;
+
+                // Update current level
+                level = rlevel;
+            }
+
+            std::shared_ptr<Node> n =
+                std::shared_ptr<Node>(new Node(key, rlevel, value));
+            for (int i = 0; i <= rlevel; i++) {
+                n->forward[i] = update[i]->forward[i];
+                update[i]->forward[i] = n;
+            }
+            std::cout << "Inserted" << std::endl;
+
+        } else {
+            std::cout << "Exists" << std::endl;
+        }
+    }
+
+    /**
+     * Deletes an element by key and prints if has been removed successfully
+     * @param key is number that is used for comparision.
+     */
+    void deleteElement(int key) {
+        std::shared_ptr<Node> x = header;
+
+        std::array<std::shared_ptr<Node>, MAX_LEVEL + 1> update;
+        update.fill(nullptr);
+
+        for (int i = level; i >= 0; i--) {
+            while (x->forward[i] != nullptr && x->forward[i]->key < key)
+                x = x->forward[i];
+            update[i] = x;
+        }
+
+        x = x->forward[0];
+
+        bool doesnt_exist = (x == nullptr || x->key != key);
+
+        if (!doesnt_exist) {
+            for (int i = 0; i <= level; i++) {
+                if (update[i]->forward[i] != x)
+                    break;
+                update[i]->forward[i] = x->forward[i];
+            }
+            /* Remove empty levels*/
+            while (level > 0 && header->forward[level] == nullptr) level--;
+            std::cout << "Deleted" << std::endl;
+        } else {
+            std::cout << "Doesn't exist" << std::endl;
+        }
+    }
+
+    /**
+     * Searching element in skip list structure
+     * @param key is number that is used for comparision
+     * @return pointer to the value of the node
+     */
+    void* searchElement(int key) {
+        std::shared_ptr<Node> x = header;
+        std::cout << "Searching for " << key << std::endl;
+
+        for (int i = level; i >= 0; i--) {
+            while (x->forward[i] && x->forward[i]->key < key) x = x->forward[i];
+        }
+
+        x = x->forward[0];
+        if (x && x->key == key) {
+            std::cout << "Found" << std::endl;
+            return x->value;
+        } else {
+            std::cout << "Not Found" << std::endl;
+            return nullptr;
+        }
+    }
+
+    /*
+     * Display skip list level
+     */
+    void displayList() {
+        std::cout << "Displaying list:\n" << std::endl;
+        for (int i = 0; i <= level; i++) {
+            std::shared_ptr<Node> node = header->forward[i];
+            std::cout << "Level " << (i) << ": ";
+            while (node != nullptr) {
+                std::cout << node->key << " ";
+                node = node->forward[i];
+            }
+            std::cout << std::endl;
+        }
+    }
 };
 
-
-/**
- * Skeep List constructor. Initializes header, start
- * Node for searching in the list
-*/
-SkipList::SkipList() { 
-    level = 0; 
-    // Header initialization
-    header = new Node(-1, MAX_LEVEL, nullptr); 
-} 
-
-/**
- * Destructor for skiplist class
-*/
-SkipList::~SkipList(){
-    for(int i=0; i <= level; i++) { 
-        Node *node = header->forward[i]; 
-        Node* temp;
-        while(node != nullptr) { 
-            temp = node;
-            node = node->forward[i];
-            delete temp;
-        } 
-    } 
-    delete header;
-}
-
-  
-/**
- * Returns random level of the skip list.
- * Every higher level is 2 times less likely.
- * @return lvl: random level for skip list;
-*/
-int SkipList::randomLevel() { 
-    int lvl = 0; 
-    while(static_cast<float>(std::rand())/RAND_MAX < PROBABILITY && lvl < MAX_LEVEL) lvl++;  
-    return lvl; 
-} 
-  
-  
-  
-/**
- * Inserts elements with given key and value;
- * It's level is computed by randomLevel() function.
- * @param key is number that is used for comparision
- * @param value pointer to a value, that can be any type
-*/
-void SkipList::insertElement(int key, void* value) { 
-    std::cout << "Inserting" << key << "...";
-    Node *x = header; 
-    Node *update[MAX_LEVEL+1]; 
-    memset(update, 0, sizeof(Node*)*(MAX_LEVEL+1)); 
-
-
-    for(int i = level; i >= 0; i--) { 
-        while(x->forward[i] != nullptr && x->forward[i]->key < key)  x = x->forward[i]; 
-        update[i] = x; 
-    } 
-
-    x = x->forward[0]; 
-
-    bool doesnt_exist = (x == nullptr || x->key != key);
-    if (doesnt_exist) { 
-        int rlevel = randomLevel(); 
-  
-        if(rlevel > level) { 
-            for(int i=level+1;i<rlevel+1;i++) update[i] = header; 
-
-            // Update current level
-            level = rlevel; 
-        } 
-  
-        Node* n = new Node(key, rlevel, value);
-        for(int i=0;i<=rlevel;i++) { 
-            n->forward[i] = update[i]->forward[i]; 
-            update[i]->forward[i] = n; 
-        } 
-        std::cout << "Inserted" << endl;
-
-    } else {
-        std::cout << "Exists" << endl;
-    }
-} 
-  
-/**
- * Deletes an element by key and prints if has been removed successfully 
- * @param key is number that is used for comparision.
-*/
-void SkipList::deleteElement(int key) { 
-    Node *x = header; 
-  
-    Node *update[MAX_LEVEL+1]; 
-    memset(update, 0, sizeof(Node*)*(MAX_LEVEL+1)); 
-  
-    for(int i = level; i >= 0; i--)  { 
-        while(x->forward[i] != nullptr  &&  x->forward[i]->key < key)  x = x->forward[i]; 
-        update[i] = x; 
-    } 
-  
-    x = x->forward[0]; 
-  
-    bool doesnt_exist = (x == nullptr || x->key != key);
-
-    if(!doesnt_exist) { 
-        for(int i=0;i<=level;i++) {
-            if(update[i]->forward[i] != x)  break; 
-            update[i]->forward[i] = x->forward[i]; 
-        }
-       /* Remove empty levels*/
-        while(level>0 &&  header->forward[level] == 0) level--; 
-        std::cout << "Deleted" << endl;
-    } else {
-        std::cout << "Doesn't exist" << endl;
-    }
-} 
-  
-
-/**
- * Searching element in skip list structure
- * @param key is number that is used for comparision
- * @return pointer to the value of the node
-*/
-void* SkipList::searchElement(int key) { 
-    Node *x = header; 
-    std::cout << "Searching for " + key << endl;
-
-    for(int i = level; i >= 0; i--) { 
-        while(x->forward[i] && x->forward[i]->key < key)  x = x->forward[i]; 
-    } 
-  
-    x = x->forward[0]; 
-    if(x && x->key == key){
-        std::cout << "Found" << endl;
-        return x->value;
-    } else {
-        std::cout << "Not Found" << endl;
-        return nullptr;
-    }
-} 
-  
-/*
- * Display skip list level
- */
-void SkipList::displayList() { 
-    std::cout << "Displaying list:\n" << endl;
-    for(int i=0; i <= level; i++) { 
-        Node *node = header->forward[i]; 
-        std::cout << "Level " << (i) << ": ";
-        while(node != nullptr) { 
-            std::cout << node->key << " ";
-            node = node->forward[i]; 
-        } 
-        std::cout << endl;
-    } 
-} 
-
+}  // namespace data_structure
 
 /**
  * Main function:
  * Creates and inserts random 2^[number of levels]
  * elements into the skip lists and than displays it
- */  
-int main() 
-{ 
+ */
+int main() {
     std::srand(std::time(nullptr));
 
-    SkipList lst;
+    data_structure::SkipList lst;
 
-    for (int j = 0; j < (1 << (MAX_LEVEL+1)); j++){
-         int k = (std::rand()%( 1 << (MAX_LEVEL+2)) + 1);
-         lst.insertElement(k, &j); 
+    for (int j = 0; j < (1 << (data_structure::MAX_LEVEL + 1)); j++) {
+        int k = (std::rand() % (1 << (data_structure::MAX_LEVEL + 2)) + 1);
+        lst.insertElement(k, &j);
     }
 
     lst.displayList();
-
-} 
+}

From c15c962f02d284f50b7a62b4af92fe2ef696a7a1 Mon Sep 17 00:00:00 2001
From: Krishna Vedala <7001608+kvedala@users.noreply.github.com>
Date: Sun, 12 Jul 2020 17:04:09 -0400
Subject: [PATCH 35/38] since we are using smart pointers, an explicit
 destructor is not required

---
 data_structures/skip_list.cpp | 16 ----------------
 1 file changed, 16 deletions(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index d7982f866..2cb78b8c8 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -67,22 +67,6 @@ class SkipList {
         header = std::shared_ptr<Node>(new Node(-1, MAX_LEVEL));
     }
 
-    /**
-     * Destructor for skiplist class
-     */
-    ~SkipList() {
-        for (int i = 0; i <= level; i++) {
-            std::shared_ptr<Node> node = header->forward[i];
-            std::shared_ptr<Node> temp;
-            while (node != nullptr) {
-                temp = node;
-                node = node->forward[i];
-                temp.reset();
-            }
-        }
-        header.reset();
-    }
-
     /**
      * Returns random level of the skip list.
      * Every higher level is 2 times less likely.

From 47f5ad9aaf0f497afec0bdcbb0138c344b9364e8 Mon Sep 17 00:00:00 2001
From: Krishna Vedala <7001608+kvedala@users.noreply.github.com>
Date: Sun, 12 Jul 2020 17:47:57 -0400
Subject: [PATCH 36/38] fix randomlevel float conversion

---
 data_structures/skip_list.cpp | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 2cb78b8c8..b1b24ea20 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -41,7 +41,7 @@ struct Node {
      * @param key is number that is used for comparision
      * @param level is the maximum level node's going to added
      */
-    Node(int key, int level, void* value = nullptr) : key(key) {
+    Node(int key, int level, void* value = nullptr) : key(key), value(value) {
         // Initialization of forward vector
         for (int i = 0; i < (level + 1); i++) {
             forward.push_back(nullptr);
@@ -74,7 +74,7 @@ class SkipList {
      */
     int randomLevel() {
         int lvl = 0;
-        while (static_cast<float>(std::rand() / RAND_MAX) < PROBABILITY &&
+        while (static_cast<float>(std::rand()) / RAND_MAX < PROBABILITY &&
                lvl < MAX_LEVEL)
             lvl++;
         return lvl;
@@ -185,7 +185,7 @@ class SkipList {
      * Display skip list level
      */
     void displayList() {
-        std::cout << "Displaying list:\n" << std::endl;
+        std::cout << "Displaying list:\n";
         for (int i = 0; i <= level; i++) {
             std::shared_ptr<Node> node = header->forward[i];
             std::cout << "Level " << (i) << ": ";

From dc4a72c4181ee000cfdfede684c089adbc3a0774 Mon Sep 17 00:00:00 2001
From: Krishna Vedala <7001608+kvedala@users.noreply.github.com>
Date: Mon, 13 Jul 2020 08:07:10 -0400
Subject: [PATCH 37/38] fix doc comment block

---
 data_structures/skip_list.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index b1b24ea20..39dda5ce6 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -181,7 +181,7 @@ class SkipList {
         }
     }
 
-    /*
+    /**
      * Display skip list level
      */
     void displayList() {

From eefe46688deb4197d14a7d123135037c7888a304 Mon Sep 17 00:00:00 2001
From: Krishna Vedala <7001608+kvedala@users.noreply.github.com>
Date: Mon, 13 Jul 2020 08:07:44 -0400
Subject: [PATCH 38/38] main function must return

---
 data_structures/skip_list.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/data_structures/skip_list.cpp b/data_structures/skip_list.cpp
index 39dda5ce6..cc679a31c 100644
--- a/data_structures/skip_list.cpp
+++ b/data_structures/skip_list.cpp
@@ -216,4 +216,6 @@ int main() {
     }
 
     lst.displayList();
+    
+    return 0;
 }