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
     */
    ListNode preHead = null;
    ListNode lastTail = null;

    public ListNode reverseBetween (ListNode head, int m, int n) {
        ListNode dummy = new ListNode(-1);
        ListNode pre = dummy;
        dummy.next = head;
        int current = 0;
        // 找到左节点
        while (current < m - 1) {
            pre = pre.next;
            current++;
        }
        preHead = pre;
        ListNode currentTail = reverseLinkedList(pre.next, m, n);
        currentTail.next = lastTail;
        return dummy.next;
    }

    public ListNode reverseLinkedList(ListNode head, int current, int n) {
        if (current == n) {
            lastTail = head.next;
            return head;
        }
        ListNode currentPre = reverseLinkedList(head.next, current + 1, n);
        if (current == n - 1) {
            preHead.next = currentPre;
        }
        currentPre.next = head;
        return head;
    }
}

采用递归方法