xyz.java

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */


class Solution {
     
    
    public ListNode reverseBetween(ListNode head, int m, int n) {
        
        if(head == null || head.next==null) return head;
        if(m==n) return head;
        int first_count = 1;
        int second_count = 1;
        ListNode temp_head = head;
        ListNode prev = null;
        ListNode next_head = head;
        
        while(first_count++!=m){
            prev = temp_head;
            temp_head = temp_head.next;
        }
        
        while(second_count++!=n){
            //prev = temp_head;
            next_head = next_head.next;
        }
        
        ListNode bam = reverseList(temp_head,n);
        ListNode end_bam = bam;
        while(end_bam.next!=null){
            end_bam = end_bam.next;
            
        }   
        
        
        
        
        
        
        prev.next = bam;
        end_bam.next = next_head.next;
        
        
        return head;
        
    }
    
    public ListNode reverseList(ListNode head, int x) {
        int xx=1;
        ListNode n = null;
        while(head!=null && xx++!=x){
            ListNode new1 = new ListNode(head.val);
            
            new1.next = n;
            n = new1;
            head = head.next;
        }
     return n;   
    }
}

ListNode bam = reverseList(temp_head, n - m + 1); // Change 1
if (prev != null) // Change 2 prev.next = bam; else head = bam; // Change 3

while(head!=null && xx++ <= x){ // Change 4