[Leetcode] Rotate List (Java)

原创于 2014-01-08 22:09:52 发布 · 559 阅读

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本文介绍了如何将给定的链表向右旋转指定的位置数。通过遍历链表计算长度，然后根据旋转次数更新链表指针实现旋转。

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.

这题写的好丑，磕磕绊绊才过

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public ListNode rotateRight(ListNode head, int n) {
		if(head==null)
			return head;
		int num = 0;
		ListNode res = new ListNode(-1);
		res.next = head;
		while(head!=null){
			num++;
			head=head.next;
		}
		n%=num;
		n=num-n;
		if(n==0)
			return head;
		head = res.next;
		int i=1;
		while(i<n){
			head=head.next;
			i++;
		}
		ListNode pre = new ListNode(-1);
		pre.next = head.next;
		if(pre.next==null)
			return res.next;
		head.next=null;
		head=pre.next;
		while(head.next!=null)
			head=head.next;
		head.next=res.next;
		return pre.next;
    }
}