Difficulty: Medium
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
Language: Java
/**
* 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 || head.next == null) {
return head;
}
int length = 0;
ListNode index = head;
while (index.next != null) {
length++;
index = index.next;
}
length++;
index.next = head; // 构建成循环链表，index 指向 head 的前一个节点
k = k % length;
for (int i = 0; i < length - k; i++) {
index = head;
head = head.next;
}
index.next = null; // 破除循环链表，添加结束 null 值
return head;
}
}