题解 | #链表内指定区间反转#

类似每k个节点反转的题

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) {

        if (head == null) {
            return head;
        }

        if (m >= n) {
            return head;
        }

        ListNode temp = head;
        int len = 0;
        while (temp != null) {
            len++;
            temp = temp.next;
        }

        ListNode headNode = new ListNode(-1);
        headNode.next = head;
        ListNode tempHeadNode = headNode;
        ListNode curNode = head;
        ListNode nextNode = null;

        for (int i = 0; i < len; i++) {

            if (i == m-1) {

                for (int j = 0; j < (n-m); j++) {
                    nextNode = curNode.next;
                    curNode.next = nextNode.next;
                    nextNode.next = tempHeadNode.next;
                    tempHeadNode.next = nextNode;
                }
                break;
            }

            tempHeadNode = curNode;
            curNode = curNode.next;        
        }

        return headNode.next;
    }
}