Merge branch 'tisha_patch1' of https://github.com/Tishasoumya-02/C-Plus-Plus into tisha_patch1

DIRECTORY.md

@@ -52,6 +52,7 @@
   * [Queue Using Linkedlist](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/data_structures/queue_using_linkedlist.cpp)
   * [Queue Using Two Stacks](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/data_structures/queue_using_two_stacks.cpp)
   * [Rb Tree](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/data_structures/rb_tree.cpp)
+  * [Reverse A Linked List](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/data_structures/reverse_a_linked_list.cpp)
   * [Skip List](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/data_structures/skip_list.cpp)
   * [Sparse Table](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/data_structures/sparse_table.cpp)
   * [Stack](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/data_structures/stack.h)

data_structures/reverse_a_linked_list.cpp

@@ -9,22 +9,23 @@
  * the pointers) starting from the first link. Whichever link points to null
  * is considered the last link and is pointed to the new value.
  *
- * Linked List can be reversed by using 3 pointers ,current ,prev and next_node ;
- * We keep iterating till the last node,meanwhile before changing to the next of current ,we store it in  the next_node pointer;
- * now we store the prev pointer in the current of next ,this is where the actual reversal happens,
- * And then we move the prev and current pointers one step forward.
- * Then the head node is made to point to the last node (prev pointer) after completion of iteration .
+ * Linked List can be reversed by using 3 pointers: current, previous, and
+ * next_node; we keep iterating until the last node. Meanwhile, before changing
+ * to the next of current, we store it in the next_node pointer, now we store
+ * the prev pointer in the current of next, this is where the actual reversal
+ * happens. And then we move the prev and current pointers one step forward.
+ * Then the head node is made to point to the last node (prev pointer) after
+ * completion of an iteration.
  */
 #include <iostream>
 
 /**
  * A Node class containing a value and pointer to next node;
  */
-class Node
-{
-public:
-    int val;    ///< value of the current link
-    Node *next; ///< pointer to the next value on the list
+class Node {
+ public:
+    int val;     ///< value of the current link
+    Node *next;  ///< pointer to the next value on the list
 };
 /**
  * function adds new element to the end of the list
@@ -32,33 +33,28 @@ public:
  * double pointer to the head node of the list to
  * reflect the changes globally in the whole program
  */
-void create(Node **head, int n)
-{
+void create(Node **head, int n) {
     Node *new_node = new Node();
-    Node *temp;
+    Node *temp = nullptr;
     new_node->val = n;
-    new_node->next = NULL;
-    if (*head == NULL)
-    {
+    new_node->next = nullptr;
+    if (*head == nullptr) {
         *head = new_node;
-    }
-    else
-    {
+    } else {
         temp = *head;
-        while (temp->next != NULL)
+        while (temp->next != nullptr) {
             temp = temp->next;
+        }
         temp->next = new_node;
     }
 }
 /**
- * function displays all the elements in the list
- * @returns 'void'
+ * @brief Utility function that displays all the elements in the list
+ * @returns void
  * @param node pointer for traversing the list.
  */
-void printList(Node *node)
-{
-    while (node != NULL)
-    {
+void printList(Node *node) {
+    while (node != nullptr) {
         std::cout << node->val << "\t";
         node = node->next;
     }
@@ -69,12 +65,10 @@ void printList(Node *node)
  * function reverseList for reversing the  list
  * @param double pointer to head node
  */
-void reverseList(Node **head)
-{
+void reverseList(Node **head) {
     Node *curr = *head;
-    Node *prev = NULL, *next_node = NULL;
-    while (curr != NULL)
-    {
+    Node *prev = nullptr, *next_node = nullptr;
+    while (curr != nullptr) {
         next_node = curr->next;
         curr->next = prev;
         prev = curr;
@@ -83,16 +77,13 @@ void reverseList(Node **head)
     *head = prev;
 }
 /**
- * Main function:
- * Allows the user add ,display and reverse values from the list.
+ * @brief Main function
  * @returns 0 on exit
  */
-int main()
-{
-    int n;
-    Node *head = NULL;
-    while (1)
-    {
+int main() {
+    int n = 0;
+    Node *head = nullptr;
+    while (true) {
         std::cout << "\n1. Insert";
         std::cout << "\n2. Display";
         std::cout << "\n3. Resverse";
@@ -100,36 +91,31 @@ int main()
         std::cout << "\n\nEnter you choice : ";
         std::cin >> n;
 
-        switch (n)
-        {
-        case 1:
-        {
-            int a;
-            std::cout << "\nEnter the element to be inserted : ";
-            std::cin >> a;
-            create(&head, a);
+        switch (n) {
+            case 1: {
+                int a = 0;
+                std::cout << "\nEnter the element to be inserted : ";
+                std::cin >> a;
+                create(&head, a);
 
-            break;
-        }
-        case 2:
-        {
-            std::cout << "Printing the Linked List\n";
-            std::cout << "\n";
-            printList(head);
+                break;
+            }
+            case 2: {
+                std::cout << "Printing the Linked List\n";
+                std::cout << "\n";
+                printList(head);
 
-            break;
-        }
-        case 3:
-        {
-            reverseList(&head);
-            break;
-        }
-        case 4:
-        {
-            exit(0);
-        }
-        default:
-            std::cout << "Invalid input\n";
+                break;
+            }
+            case 3: {
+                reverseList(&head);
+                break;
+            }
+            case 4: {
+                exit(0);
+            }
+            default:
+                std::cout << "Invalid input\n";
         }
     }
     return 0;