p61

LeetCode p61 Rotate List 题解

1.题目：

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.

题意：

输入一个链表转置它末尾的K个数。

2.解题思路:

见代码，输入的K可能会超过链表长度。

3.代码

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[title] [] [url] [link text]

 
/**
 * 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 || k == 0)
			return head;
		int count = 0;
		ListNode fast = head;
		ListNode slow = head;
		while (fast != null) {
			fast = fast.next;
			count++;
		}
		count = k % count;
		if (count == 0)
			return head;
		fast = head;
		while (count > 0 && fast != null) {
			fast = fast.next;
			count--;
		}
		if (fast == null)
			return head;
		while (fast.next != null) {
			fast = fast.next;
			slow = slow.next;
		}
		ListNode ans = slow.next;
		fast.next = head;
		slow.next = null;
		return ans;
    }
}

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4.一些总结：