Leetcode[Easy] - Remove Nth Node From End of List

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public ListNode removeNthFromEnd(ListNode head, int n) {
        ListNode prev,current = head;
        int count=0;
        while(current != null){
            count ++;
            current = current.next;
        }
        
        int k=count-n;
        current = head; 
        prev = head;
        for(int i=0 ; i<k; i++ )
        {   
            prev = current;
            current = current.next;
        }
        
        if(prev == current)
        {
            prev = current.next;
            head = prev;
        }
        else
           prev.next = current.next;
           
        return head;
    }

}

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Given a linked list, remove the nth node from the end of list and return its head.

For example,

   Given linked list: 1->2->3->4->5, and n = 2.

   After removing the second node from the end, the linked list becomes 1->2->3->5.

Note:
Given n will always be valid.
Try to do this in one pass.