题解 | #链表内指定区间反转#

/*
 * 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
        if(m == n){
            return head;
        }
        ListNode newHead = new ListNode(-1);
        newHead.next = head;
        ListNode pre = newHead;
        ListNode cur = head;
        for(int i = 1;i < m; i++){
            pre = cur;
            cur = cur.next;
        }
        for(int i = m; i < n;i ++){
            ListNode node = cur.next;  
            cur.next = node.next; //2->4
            node.next = pre.next; //3->2
            pre.next = node;      //1->3
        }
        return newHead.next;
    }
}