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 tempreNode = new ListNode(0);
        tempreNode.next = head;
        ListNode head1 = tempreNode;
        ListNode index = tempreNode;
        ListNode mHead = tempreNode;
        ListNode mHead1Index = tempreNode;
        ListNode nTail = tempreNode;
        ListNode mPre = tempreNode;
    

        if(m == 1&&n == 1){
          return head;
        }

        for(int i = 0;i<=n ;i++){
            
            if(i == m){
                mHead = head1;
                index = head1;
                mHead1Index = head1;
            }
            if(i == n){
                nTail = head1;      
            }
            if(i == m-1){
                mPre = head1;
            }
            head1 = head1.next;
        }
        ListNode tail = nTail.next;
    
        mPre.next = null;
    
        nTail.next = null;
        
        while(index!=nTail){
            index = index.next;
            mHead.next = null;
            if(nTail.next == null){
            nTail.next = mHead;
            }else{
             mHead.next = nTail.next;
             nTail.next = mHead;
            }
            mHead = index;
        }
        
        mHead1Index.next = tail;
        mPre.next = index; 
        
        return tempreNode.next;



        // write code here
    }
}