61. Rotate List

Given the head of a linked list, rotate the list to the right by k places.

Example 1:
Input: head = [1,2,3,4,5], k = 2
Output: [4,5,1,2,3]

Example 2:
Input: head = [0,1,2], k = 4
Output: [2,0,1]

Constraints:
The number of nodes in the list is in the range [0, 500].
-100 <= Node.val <= 100
0 <= k <= 2 * 109

Solution:

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode rotateRight(ListNode head, int k) {
        if (head == null) return null;
        int len = 1;
        ListNode newHead = head;
        while (newHead.next != null) {
            newHead = newHead.next;
            len++;
        }
        newHead.next = head;
        for (int i = len-k % len; i > 1; i--) {
            head = head.next;
        }
        newHead = head.next;
        head.next = null;
        return newHead;
    }
}

references

https://leetcode.com/problems/rotate-list/

# java, linked list, medium

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