Find the Kth to The Last Node of a Singly Link List

FindKthNodeFromEnd.cs

public class Solution{
  
  public ListNode FindKthNode(ListNode head, int n){
    
    if(head == null || n <= 0) return null;
    
    ListNode fast = head;

    //Verify what is Kth to the last
    // 1 -> 2 -> 3 and k = 1, if K = 3 or K = 2. For now assume the former is correct
    int stepAhead = n - 1;
    
    for(int i = 0; i < stepAhead; i++){
      if(fast.next == null)
        return null;
      fast = fast.next;
    }
    
    ListNode current = head;
    
    while(fast != null){
      fast = fast.next;
      current = current.next;
    }
    
    return current;
  }
}