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) return head;
        List<ListNode> nodeList = new ArrayList<>();
        nodeList.add(head);
        ListNode target1 = head;
        while (true) {
            ListNode next = target1.next;
            if (next == null) break;
            nodeList.add(next);
            target1 = next;
        }

        m = m - 1;
        n = n - 1;
        if (m == n && m <= nodeList.size()) {
            return head;
        }
        if (m >= 0 && n < nodeList.size() && m < n) {

            for (int i = n; i > m; i--) {
                ListNode nextTarget = nodeList.get(i);
                if (i > 0) {
                    ListNode nextTarget1 = nodeList.get(i - 1);
                    nextTarget1.next = null;
                    nextTarget.next = nextTarget1;
                }
            }
            ListNode body = nodeList.get(n);
            ListNode mBody = nodeList.get(m);
            if (m > 0) {
                ListNode start = nodeList.get(m - 1);
                start.next = body;
                if (n < nodeList.size() - 1) {
                    ListNode end = nodeList.get(n + 1);
                    mBody.next = end;
                }
                return nodeList.get(0);
            } else {
                if (n < nodeList.size() - 1) {
                    ListNode end = nodeList.get(n + 1);
                    mBody.next = end;
                }
                return nodeList.get(n);
            }
        }

        return null;
    }
}