LeetCode 61: Rotate List Solution
Master LeetCode problem 61 (Rotate List), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.
61. Rotate List
Problem Explanation
Explanation
To rotate a linked list to the right by k places, we can follow these steps:
- Find the length of the linked list and calculate the actual rotation amount by taking the remainder of k divided by the length.
- Connect the last node to the head node to form a circular linked list.
- Find the new tail node at position length - actual rotation amount - 1 and set the new head node to the next node.
- Break the circular list by setting the new tail node's next to null.
Time complexity: O(n) where n is the number of nodes in the linked list. Space complexity: O(1)
Solution Code
public ListNode rotateRight(ListNode head, int k) {
if (head == null || head.next == null || k == 0) {
return head;
}
int length = 1;
ListNode current = head;
while (current.next != null) {
length++;
current = current.next;
}
int actualRotation = k % length;
if (actualRotation == 0) {
return head;
}
current.next = head; // form a circular linked list
ListNode newTail = head;
for (int i = 0; i < length - actualRotation - 1; i++) {
newTail = newTail.next;
}
ListNode newHead = newTail.next;
newTail.next = null; // break the circular list
return newHead;
}Try It Yourself
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