Day70.java

class ListNode {
    int val;
    ListNode next;
    ListNode(int val) {
        this.val = val;
        this.next = null;
    }
}


public class Day70 {
    public ListNode removeNthFromEnd(ListNode head, int k) {
        ListNode dummy = new ListNode(0);
        dummy.next = head;
        ListNode slow = dummy;
        ListNode fast = dummy;
        
        for (int i = 0; i <= k; i++) {
            if (fast == null)
                return head;
            fast = fast.next;
        }
        
        while (fast != null) {
            slow = slow.next;
            fast = fast.next;
        }
        
        slow.next = slow.next.next;
        
        return dummy.next;
    }
    public static void main(String[] args) {
        RemoveKthNode solution = new RemoveKthNode();
        
        // Example usage
        ListNode head = new ListNode(1);
        head.next = new ListNode(2);
        head.next.next = new ListNode(3);
        head.next.next.next = new ListNode(4);
        
        int k = 2;
        ListNode result = solution.removeNthFromEnd(head, k);
        
        while (result != null) {
            System.out.print(result.val + " -> ");
            result = result.next;
        }
        System.out.println("NULL");
    }
}