[leetcode]92. Reverse Linked List II反转链表2

Reverse a linked list from position m to n. Do it in one-pass.

Note: 1 ≤ m ≤ n ≤ length of list.

Example:

Input: 1->2->3->4->5->NULL, m = 2, n = 4
Output: 1->4->3->2->5->NULL

题意：

给定一个链表，反转第m~n个节点。

反转链表的一般思路

Solution1：

1.用指针找到m和n位置

2.反转m和n之间的链表

code

class Solution {
    public ListNode reverseBetween(ListNode head, int m, int n) {
         if(head==null) return head;

        ListNode dummy = new ListNode(-1);

        dummy.next = head;

        ListNode mNode = head;
        ListNode preM = dummy;
        ListNode nNode = head;

        for (int i = 1; i < m ; i++) {
            preM = mNode;
            mNode = mNode.next;
        }

        for (int i = 1; i <n ; i++) {
            nNode = nNode.next;
        }

        while(mNode != nNode){
            preM.next = mNode.next;
            mNode.next = nNode.next;
            nNode.next = mNode;
            mNode = preM.next;    
        }
        return dummy.next;   
    }
}