Leetcode92. 反转链表 II

92. 反转链表 II

Difficulty: 中等

反转从位置 m 到 n 的链表。请使用一趟扫描完成反转。

说明:
1 ≤ m ≤ n ≤ 链表长度。

示例:

输入: 1->2->3->4->5->NULL, m = 2, n = 4
输出: 1->4->3->2->5->NULL

Solution

Language: java

​/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode reverseBetween(ListNode head, int left, int right) {
        ListNode t = head, pre = null;
        for(int i=1; i<left; i++){
            pre = t;
            t = t.next;
        }
        ListNode end = t, start = t;
        for(int i=0; i<right-left; i++){
            ListNode tmp = t.next;
            t.next = tmp.next;
            tmp.next = start;
            start = tmp;
        }
        if(pre == null) head = start;
        else pre.next = start;
        return head;
    }
}