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.

Analysis

• 注意k可能大于list总长度，需要取%

Code

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode rotateRight(ListNode head, int k) {
        if (head==null || head.next==null) {return head;}
        ListNode dummy = new ListNode(0);
        dummy.next = head;
        ListNode fast=dummy, slow=dummy;

        //get the total length of list
        int i;
        for (i=0; fast.next!=null; i++) {fast = fast.next;}

        //move slow to the node before rotation
        for(int j=i-k%i; j>0;j--) {slow = slow.next;}

        //do rotation
        fast.next = dummy.next;
        dummy.next = slow.next;
        slow.next = null;

        return dummy.next;
    }
}

Reference

Leetcode