Leetcode61 Rotate List

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.

Solution

• 利用两个指针定位到需要翻转的地方。

public class Solution {
    public ListNode rotateRight(ListNode head, int k) {
        if(head==null) return head;
        ListNode dummy = new ListNode(-1);
        dummy.next = head;
        ListNode fast = head;
        ListNode slow = head;
        int count;
        for(count=0;fast!=null;fast=fast.next) count++;
        k %= count;
        if(k==0) return head;
        for(fast=head;k-->0;fast = fast.next);
        for(;fast.next!=null;fast=fast.next,slow=slow.next);
        fast.next = dummy.next;
        dummy.next = slow.next;
        slow.next = null;
        return dummy.next;        
    }
}