61.Rotate-List

61. Rotate List

题目地址

题目描述

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