题解 | #链表内指定区间反转#

1.找到反转前一个节点，可以构造一个虚拟节点，指向下个节点 2.反转节点 3.连接2处节点

import java.util.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 * }
 */

public class Solution {
    /**
     * 
     * @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) {
        ListNode pn = null, pm = null;
        ListNode p = new ListNode(-1);
        p.next = head;
        ListNode p1 = p;

        int i = 0;
        while (i+1 != m) {
            p1 = p1.next;
            i++;
        }

        ListNode p2 = p1.next;
        ListNode p3 = null, p5 = p2;
        while(i != n) {
            ListNode next = p2.next;
            p2.next = p3;
            p3 = p2;
            p2 = next;
            i++;
        }
        p1.next = p3;
        p5.next = p2;
        return p.next;
    }
}