mines

/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) {
* val = x;
* next = null;
* }
* }
*/
public class Solution {
	public ListNode reverseBetween(ListNode head, int m, int n) {
		// Start typing your Java solution below
		// DO NOT write main() function

		ListNode first=head;
		int i=1;
		ListNode start=first, startParent=null, temp=null, curr=null, prev=null;

		if(m==0 || n==0 || m>=n || first==null || first.next==null)
		{
			return first;
		}
                //start will store the mth element, curr and prev are just used for iteration
		while(i<m){
			startParent = start;
			start = start.next();
			i++;
		}

		prev = start;
		curr = prev.next;
		while(i<=n){
			temp = curr.next;
			curr.next = prev;
			prev = curr;
			curr = temp;
		}
		//prev will be pointing to nth element
		//curr will be pointing to nth child

		startParent.next = prev;
		start.next = curr;
		return first;
	}
}

shalkisCode

/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) {
* val = x;
* next = null;
* }
* }
*/
public class Solution {
	public ListNode reverseBetween(ListNode head, int m, int n) {
		// Start typing your Java solution below
		// DO NOT write main() function

		ListNode first=head;
		int i=1;
		ListNode curr=first, curr1=null, prev=null, prev1=null, temp=null;

		if(m==0 || n==0 || m>=n || first==null || first.next==null)
		{
			return first;
		}

		if(m==1)
		{
			prev1=null;
			curr=first;
			curr1=curr;
			prev=curr;
			curr=curr.next;
			i++;
		} else{
			while(i<m)
			{
				prev=curr;
				curr=curr.next;
				i++;
			}
			prev1=prev;
			curr1=curr;
		}

		if(n==m+1)
		{
			temp=curr.next;
			curr.next=prev;
			prev1.next=curr;
			curr1.next=temp;
		} else{
			while(i<n)
			{
				temp=curr.next;
				curr.next=prev;

				prev=curr;
				curr=curr.next;
			}

			prev1.next=curr;
			curr1.next=curr.next;
		}
		if(m==1)
			first=curr;

		return first;
	}
}