92. Reverse Linked List II

题目

原始地址:https://leetcode.com/problems/reverse-linked-list-ii/#/description

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode reverseBetween(ListNode head, int m, int n) {
        
    }
}

描述

局部翻转一个单链表,从m到n。要求原地调整并且只能遍历一次。

分析

这个题目的思路比较好理解,首先找到第m-1个节点,然后反转第m到n个节点,最后再将前m-1个节点,反转后的第m到第n节点以及n之后的节点分别连起来即可。

解法

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode reverseBetween(ListNode head, int m, int n) {
        ListNode dummy = new ListNode(0), prev, curr, next = null, start = dummy, end;
        dummy.next = head;
        for (int i = 0; i < m - 1; i++) {
            start = start.next;
        }
        end = start.next;
        prev = null;
        curr = start.next;
        for (int i = m; i <= n; i++) {
            next = curr.next;
            curr.next = prev;
            prev = curr;
            curr = next;
        }
        start.next = prev;
        end.next = next;
        return dummy.next;
    }
}
posted @ 2017-05-09 14:21  北冥尝有鱼  阅读(80)  评论(0编辑  收藏  举报