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) {
        ListNode dummy = new ListNode(-1);
        dummy.next = head;
        ListNode b = dummy;
        for (int i=0; i<m-1; i++) {
            b = b.next;
        }
        ListNode e = dummy;
        for (int i=0; i<n+1; i++) {
            e = e.next;
        }
        ListNode cur = b.next;
        ListNode prev = e;
        while (cur != e) {
            ListNode next = cur.next;
            cur.next = prev;
            prev = cur;
            cur = next;
        }
        b.next = prev;
        return dummy.next;
    }
}