05_RemoveNthFromEnd.java

// Problem: Remove Nth Node From End of Linked List
// Author: Ataul (codeByunique)

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

class RemoveNthFromEnd {
    public static void main(String[] args) {
        // Linked List: 1 → 2 → 3 → 4 → 5
        ListNode head = new ListNode(1);
        head.next = new ListNode(2);
        head.next.next = new ListNode(3);
        head.next.next.next = new ListNode(4);
        head.next.next.next.next = new ListNode(5);

        int n = 2;
        ListNode newHead = removeNthFromEnd(head, n);

        // Print updated list
        while (newHead != null) {
            System.out.print(newHead.val + " ");
            newHead = newHead.next;
        }
    }

    public static ListNode removeNthFromEnd(ListNode head, int n) {
        ListNode dummy = new ListNode(0);
        dummy.next = head;
        ListNode first = dummy;
        ListNode second = dummy;

        // Move first n+1 steps ahead
        for (int i = 0; i <= n; i++) {
            first = first.next;
        }

        // Move both pointers
        while (first != null) {
            first = first.next;
            second = second.next;
        }

        // Remove the nth node
        second.next = second.next.next;

        return dummy.next;
    }
}