61.Rotate-List

61. Rotate List

题目地址

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

题目描述

Given a linked list, rotate the list to the right by k places, where k is non-negative.

Example 1:
Input: 1->2->3->4->5->NULL, k = 2
Output: 4->5->1->2->3->NULL
Explanation:
rotate 1 steps to the right: 5->1->2->3->4->NULL
rotate 2 steps to the right: 4->5->1->2->3->NULL

Example 2:
Input: 0->1->2->NULL, k = 4
Output: 2->0->1->NULL
Explanation:
rotate 1 steps to the right: 2->0->1->NULL
rotate 2 steps to the right: 1->2->0->NULL
rotate 3 steps to the right: 0->1->2->NULL
rotate 4 steps to the right: 2->0->1->NULL

代码

Approach #1

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
  public ListNode rotateRight(ListNode head, int k) {
        if (head == null)        return null;
    if (head.next == null)        return head;

    ListNode tail = head;
    while (tail.next != null) {
      tail = tail.next;
    }
    tail.next = head;

    ListNode node = head;
    for (int i = 0; i < n - k % n - 1; i++) {
      node = node.next;
    }
    ListNode newHead = node.next;
    node.next = null;

    return newHead;
  }
}