Add rotate_linkedlist.cpp – rotate singly linked list by k nodes

rotate_linkedlist.cpp

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+// filename: rotate_linkedlist.cpp
+// Compile: g++ rotate_linkedlist.cpp -o rotate_linkedlist
+// Run: ./rotate_linkedlist
+// Author: mnvrohith
+// Date: 22-10-2025
+// Description:
+// A simple C++ implementation of rotating a singly linked list
+// by k nodes. The linked list is implemented using a Node struct
+// and LinkedList class with addFirst, display, and rotate methods.
+
+
+#include <iostream>
+using namespace std;
+
+// Node structure for linked list
+struct Node {
+    int data;
+    Node* next;
+};
+
+class LinkedList {
+    Node* head; // Pointer to the head of the list
+public:
+    LinkedList() { head = nullptr; }
+
+    // Add a new node at the beginning of the list
+    void addFirst(int x) {
+        Node* temp = new Node();
+        temp->data = x;
+        temp->next = head;
+        head = temp;
+    }
+
+    // Rotate the linked list by k nodes
+    void rotate(int k) {
+        if (head == nullptr || k <= 0) return;
+
+        // Count total nodes
+        Node* temp = head;
+        int length = 1;
+        while (temp->next != nullptr) {
+            temp = temp->next;
+            length++;
+        }
+
+        // Connect last node to head to make it circular
+        temp->next = head;
+
+        // Adjust k if k > length
+        k = k % length;
+        if (k == 0) {
+            temp->next = nullptr; // break circular link
+            return;
+        }
+
+        // Traverse to find the new tail (k-th node)
+        Node* newTail = head;
+        for (int i = 1; i < k; i++) {
+            newTail = newTail->next;
+        }
+
+        // Set new head and break circular link
+        head = newTail->next;
+        newTail->next = nullptr;
+    }
+
+    // Print the linked list
+    void display() {
+        Node* temp = head;
+        cout << "Linked List: ";
+        while (temp != nullptr) {
+            cout << temp->data << "->";
+            temp = temp->next;
+        }
+        cout << "NULL" << endl;
+    }
+};
+
+int main() {
+    LinkedList ll;
+
+    // Create sample linked list: 1->2->3->4->5->6
+    ll.addFirst(6);
+    ll.addFirst(5);
+    ll.addFirst(4);
+    ll.addFirst(3);
+    ll.addFirst(2);
+    ll.addFirst(1);
+
+    cout << "Original Linked List:" << endl;
+    ll.display();
+
+    int k = 2;
+    ll.rotate(k);
+
+    cout << "Linked List after rotating by " << k << " nodes:" << endl;
+    ll.display();
+
+    return 0;
+}