[GSSoc 2023] Linked list changes

Linked List/Middle_of_Linked_List.md

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+## Description
+Traversing the linked list with 2 pointers to find the middle node of the linked list.
+
+## Code
+```cpp
+#include <bits/stdc++.h>
+using namespace std;
+
+struct ListNode {
+    int val;
+    ListNode* next;
+
+    ListNode(int value) : val(value), next(nullptr) {}
+};
+
+//Also Known as tortoise hare method where we use a fast pointer and a slow pointer
+ListNode* findMiddle(ListNode* head) {
+    if (head == nullptr || head->next == nullptr)
+        return head;
+
+    ListNode* slow = head;
+    ListNode* fast = head;
+
+    while (fast != nullptr && fast -> next != nullptr) {
+        slow = slow -> next; //Traverse 1 node at a time
+        fast = fast -> next -> next; //Traverse 2 nodes at a time
+    }
+
+    return slow; //Finally the middle node will be stored in slow
+}
+
+int main() {
+    // Create a sample linked list
+    ListNode* head = new ListNode(1);
+    ListNode* node2 = new ListNode(2);
+    ListNode* node3 = new ListNode(3);
+    ListNode* node4 = new ListNode(4);
+    ListNode* node5 = new ListNode(5);
+
+    head -> next = node2;
+    node2 -> next = node3;
+    node3 -> next = node4;
+    node4 -> next = node5;
+
+    // Find the middle of the linked list
+    ListNode* middle = findMiddle(head);
+
+    if (middle != nullptr)
+        cout << "Middle element: " << middle -> val << endl;
+    else
+        cout << "Linked list is empty." << endl;
+
+    // Clean up the memory
+    ListNode* current = head;
+    while (current != nullptr) {
+        ListNode* next = current->next;
+        delete current;
+        current = next;
+    }
+
+    return 0;
+}
+```
+## Run Code
+https://ide.geeksforgeeks.org/online-cpp14-compiler/76385d10-1474-41ca-8859-ec5293448563
+
+## Complexities
+### Time Complexity  :
+O(n)
+### Space Complexity  :
+O(1)
+