Merge pull request #772 from SamratDe/fix-issue

fix #765: Doubly Linked List algorithm bug

data_structure/Doubly Linked List.cpp

@@ -1,134 +0,0 @@
-#include <iostream>
-using namespace std;
-
-struct node
-{
-	int val;
-	node *prev;
-	node *next;
-};
-
-node *start;
-
-void insert(int x)
-{
-	node *t = start;
-	if (start != NULL)
-	{
-		while (t->next != NULL)
-		{
-			t = t->next;
-		}
-		node *n = new node;
-		t->next = n;
-		n->prev = t;
-		n->val = x;
-		n->next = NULL;
-	}
-	else
-	{
-		node *n = new node;
-		n->val = x;
-		n->prev = NULL;
-		n->next = NULL;
-		start = n;
-	}
-}
-
-void remove(int x)
-{
-	node *t = start;
-	while (t->val != x)
-	{
-		t = t->next;
-	}
-	t->prev->next = t->next;
-	t->next->prev = t->prev;
-	delete t;
-}
-
-void search(int x)
-{
-	node *t = start;
-	int found = 0;
-	while (t != NULL)
-	{
-		if (t->val == x)
-		{
-			cout << "\nFound";
-			found = 1;
-			break;
-		}
-		t = t->next;
-	}
-	if (found == 0)
-	{
-		cout << "\nNot Found";
-	}
-}
-
-void show()
-{
-	node *t = start;
-	while (t != NULL)
-	{
-		cout << t->val << "\t";
-		t = t->next;
-	}
-}
-
-void reverseShow()
-{
-	node *t = start;
-	while (t->next != NULL)
-	{
-		t = t->next;
-	}
-	while (t != NULL)
-	{
-		cout << t->val << "\t";
-		t = t->prev;
-	}
-}
-
-int main()
-{
-	int choice, x;
-	do
-	{
-		cout << "\n1. Insert";
-		cout << "\n2. Delete";
-		cout << "\n3. Search";
-		cout << "\n4. Forward print";
-		cout << "\n5. Reverse print";
-		cout << "\n\nEnter you choice : ";
-		cin >> choice;
-		switch (choice)
-		{
-		case 1:
-			cout << "\nEnter the element to be inserted : ";
-			cin >> x;
-			;
-			insert(x);
-			break;
-		case 2:
-			cout << "\nEnter the element to be removed : ";
-			cin >> x;
-			remove(x);
-			break;
-		case 3:
-			cout << "\nEnter the element to be searched : ";
-			cin >> x;
-			search(x);
-			break;
-		case 4:
-			show();
-			break;
-		case 5:
-			reverseShow();
-			break;
-		}
-	} while (choice != 0);
-
-	return 0;
-}

data_structure/doubly_linked_list.cpp

@@ -0,0 +1,137 @@
+#include <iostream>
+#include<cstdio>
+#include<cstdlib>
+
+struct node {
+  int val;
+  node *prev;
+  node *next;
+}*start;
+
+class double_linked_list {
+ public:
+  double_linked_list() {
+    start = NULL;
+  }
+  void insert(int x);
+  void remove(int x);
+  void search(int x);
+  void show();
+  void reverseShow();
+};
+
+void double_linked_list::insert(int x) {
+  node *t = start;
+  if (start != NULL) {
+    while (t->next != NULL) {
+      t = t->next;
+    }
+    node *n = new node;
+    t->next = n;
+    n->prev = t;
+    n->val = x;
+    n->next = NULL;
+  } else {
+    node *n = new node;
+    n->val = x;
+    n->prev = NULL;
+    n->next = NULL;
+    start = n;
+  }
+}
+
+void double_linked_list::remove(int x) {
+  node *t = start;
+  while (t != NULL && t->val != x) {
+    t = t-> next;
+  }
+  if (t == NULL) {
+    return;
+  }
+  if (t->prev == NULL) {
+    if (t->next == NULL) {
+      start = NULL;
+    } else {
+      start = t->next;
+      start->prev = NULL;
+    }
+  } else if (t->next == NULL) {
+    t->prev->next = NULL;
+  } else {
+    t->prev->next = t->next;
+    t->next->prev = t->prev;
+  }
+}
+
+void double_linked_list::search(int x) {
+  node *t = start;
+  int found = 0;
+  while (t != NULL) {
+    if (t->val == x) {
+      std::cout << "\nFound";
+      found = 1;
+      break;
+    }
+    t = t->next;
+  }
+  if (found == 0) {
+    std::cout << "\nNot Found";
+  }
+}
+
+void double_linked_list::show() {
+  node *t = start;
+  while (t != NULL) {
+    std::cout << t->val << "\t";
+    t = t->next;
+  }
+}
+
+void double_linked_list::reverseShow() {
+  node *t = start;
+  while (t != NULL && t->next != NULL) {
+    t = t->next;
+  }
+  while (t != NULL) {
+    std::cout << t->val << "\t";
+    t = t->prev;
+  }
+}
+
+int main() {
+  int choice, x;
+  double_linked_list ob;
+  do {
+    std::cout << "\n1. Insert";
+    std::cout << "\n2. Delete";
+    std::cout << "\n3. Search";
+    std::cout << "\n4. Forward print";
+    std::cout << "\n5. Reverse print";
+    std::cout << "\n\nEnter you choice : ";
+    std::cin >> choice;
+    switch (choice) {
+      case 1:
+        std::cout << "\nEnter the element to be inserted : ";
+        std::cin >> x;
+        ob.insert(x);
+        break;
+      case 2:
+        std::cout << "\nEnter the element to be removed : ";
+        std::cin >> x;
+        ob.remove(x);
+        break;
+      case 3:
+        std::cout << "\nEnter the element to be searched : ";
+        std::cin >> x;
+        ob.search(x);
+        break;
+      case 4:
+        ob.show();
+        break;
+      case 5:
+        ob.reverseShow();
+        break;
+    }
+  } while (choice != 0);
+  return 0;
+}