leetcode : Rotate List

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

For example:
Given 1->2->3->4->5->NULL and k = 2,
return 4->5->1->2->3->NULL.

思路：

（1）先求出链表的长度length

（2） k%length 防止k大于length

（3）慢指针指向倒数第k+1，快指针指向最后一个节点

/*** Definition for singly-linked list.* public class ListNode {*     int val;*     ListNode next;*     ListNode(int x) { val = x; }* }*/
public class Solution {private int getLength(ListNode head) {int length = 0;while(head != null) {length++;head = head.next;}return length;}public ListNode rotateRight(ListNode head, int k) {if(head == null) {return head;}ListNode dummy =new ListNode(0);dummy.next = head;ListNode fast = head;int length = getLength(head);k = k % length;while(k > 0) {fast = fast.next;k--;}while(fast.next != null) {fast = fast.next;head = head.next;}// 此时 fast 指向最后一个节点， head 指向倒数第k+1个节点fast.next = dummy.next;dummy.next = head.next;head.next = null;return dummy.next;}
}

转载于:https://www.cnblogs.com/superzhaochao/p/6479083.html

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