题解 | #链表内指定区间反转#

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) {
        // write code here
        ListNode newHead = new ListNode(-1);
        newHead.next = head;
        ListNode pre = newHead;
        for (int i = 0; i < m - 1; i++, n--) {
            pre = pre.next;
        }
        ListNode cur = pre.next;//找到需要断开的结点头
        pre.next = null;
        ListNode rHead = cur;
        for (int i = 0; i < n - 1; i++) {
            rHead = rHead.next;
        }
        ListNode tail = rHead.next;//找到需要断开的结点尾
        rHead.next = null;
	  //将中间断开的链表进行反转
        ListNode newPre = null;
        ListNode rTail = cur;
        while (cur != null) {
            ListNode temp = cur.next;
            cur.next = newPre;
            newPre = cur;
            cur = temp;
        }
	 //反转之后，再链接到一起
        pre.next = newPre;
        rTail.next = tail;
        return newHead.next;
    }
}