19. Remove Nth Node From End of List

/**
 * Definition for singly-linked list.
 * public class ListNode
  {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution 
{
    private static int size(ListNode head)
    {
        int cnt=0;
        ListNode temp = head;
        while(temp!=null)
        {
            cnt++;
            temp=temp.next;
            
        }
        return cnt;
    }
    
    
    public ListNode removeNthFromEnd(ListNode head, int n) 
    {
        if(head == null || head.next==null)
        return null;
         
        int sz=size(head);
        if(n==sz)
        {
            head=head.next;
            return head;
        }

      

         if(head.next.next == null && n==2)
         {
            head=head.next;
            return head;
         }
        



        ListNode temp = head;
        for(int i=1 ; i< sz-n ; i++)
        {
            temp=temp.next;
        }
        temp.next = temp.next.next;
        return head;


        
    }
}