题解 | 链表内指定区间反转

import java.util.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 *   public ListNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param head ListNode类 
     * @param m int整型 
     * @param n int整型 
     * @return ListNode类
     */
    public ListNode reverseBetween (ListNode head, int m, int n) {
        // write code here
        if(head == null || m == n )
        {
            return head;
        }
        ListNode dumy = new ListNode(-1);
        dumy.next = head;
        ListNode pre = dumy;
        for(int i = 1 ; i < m ; i++)
        {
            pre = pre.next;
        }
        ListNode cur = pre.next;
        for(int i = 0 ; i < n - m ; i ++)
        {
            ListNode nextTemp = cur.next;
            cur.next = nextTemp.next;
            nextTemp.next = pre.next;
            pre.next = nextTemp;
        }
        return dumy.next;       
    }
}