Merge pull request Pradeepsingh61#604 from harshitpandey-26/patch-5

Create rotateList.js

Author: Pradeepsingh61

JavaScript/data_structures/linkedLists/rotateList.js

@@ -0,0 +1,60 @@
+// Author: HarshitKumarPandey
+// Date: 2025-10-09
+// Description: Rotate a singly linked list to the right by k positions.
+
+class ListNode {
+  constructor(val = 0, next = null) {
+    this.val = val;
+    this.next = next;
+  }
+}
+
+function rotateRight(head, k) {
+  if (!head || !head.next || k === 0) return head;
+
+  // Step 1: Find the length of the list
+  let length = 1;
+  let tail = head;
+  while (tail.next) {
+    tail = tail.next;
+    length++;
+  }
+
+  // Step 2: Make it circular
+  tail.next = head;
+
+  // Step 3: Find new tail: (length - k % length - 1)th node
+  k = k % length;
+  let stepsToNewHead = length - k;
+  let newTail = tail;
+  while (stepsToNewHead-- > 0) {
+    newTail = newTail.next;
+  }
+
+  const newHead = newTail.next;
+  newTail.next = null; // break the circle
+
+  return newHead;
+}
+
+// Helper function to print linked list
+function printList(head) {
+  const values = [];
+  let curr = head;
+  while (curr) {
+    values.push(curr.val);
+    curr = curr.next;
+  }
+  console.log(values.join(" -> "));
+}
+
+// Example usage
+const head = new ListNode(1, new ListNode(2, new ListNode(3, new ListNode(4, new ListNode(5)))));
+const k = 2;
+
+console.log("Original List:");
+printList(head);
+
+const rotated = rotateRight(head, k);
+console.log("Rotated List:");
+printList(rotated); // Output: 4 -> 5 -> 1 -> 2 -> 3