class IntNode{
    int value;
    IntNode next;

    IntNode(int value, IntNode restOfTheList){
        this.value = value;
        this.next = restOfTheList;
    }
}

class Solution {
    IntNode head;

    Solution(IntNode head) {
        this.head = head;
    }

    static Solution fromArray(int[] arr) {
        // create a linked list with IntNodes

        int arrLength = arr.length;

        IntNode front = null;

        for (int i = arrLength - 1; i >= 0; i--) {
            front = new IntNode(arr[i], front);
        }

        return new Solution(front);
    }

    void print() {
        IntNode iterator = head;

        while (iterator!=null) {
            System.out.print(iterator.value + " -> ");
            iterator = iterator.next;
        }

        System.out.println("null");
    }

    Solution drop(int toDrop) {
        IntNode iterator = head;

        while (toDrop > 0 && iterator != null) {
            iterator = iterator.next;
            toDrop--;
        }

        return new Solution(iterator);
    }

    // IntNode reverse(IntNode node){
    //     if(node == null)return null;

    //     node.next = reverse(node.next);
    //     node.next.next = node;
    // }

    Solution take(int toTake) {
        if(toTake == 0){
            return new Solution(null);
        }

        if(head == null)return this;

        IntNode restOfTheList = new Solution(head.next).take(toTake - 1).head;
        return new Solution(new IntNode(head.value, restOfTheList));

        // IntNode iterator = head;

        // IntNode front = null;
        // // 1 2 3 4 5 ( 3 )
        // while (toTake > 0 && iterator != null) {
        //     front = new IntNode(iterator.value, front);
        //     iterator = iterator.next;
        //     toTake--;
        // } // 3 2 1

        // return new Solution(front);
    }

    Solution last(int toTakeLast) {
        // 1 2 3 4 5 6 7 8 null
        //             ^   ^

        // 3
        // 1, 3
        //

        IntNode iterator = head;

        while (toDrop > 0 && iterator != null) {
            iterator = iterator.next;
            toDrop--;
        }

        return new Solution(iterator);
    }


    public static void main(String[] args) {
        Solution empty = Solution.fromArray(new int[] {});
        Solution list1 = Solution.fromArray(new int[] { 1, 2, 3 });
        Solution list2 = Solution.fromArray(new int[] { 1, 2, 3, 4, 5 });

        // empty.drop(1).print(); // null
        // list1.drop(4).print(); // null
        // list1.drop(0).print(); // 1 -> 2 -> 3 -> null
        // list2.drop(2).print(); // 3 -> 4 -> 5 -> null

        // empty.take(1).print(); // null
        // list2.take(0).print(); // null
        // list1.take(4).print(); // 1 -> 2 -> 3 -> null
        // list2.take(3).print(); // 1 -> 2 -> 3 -> null

        empty.last(1).print(); // null
        list2.last(0).print(); // null
        list1.last(4).print(); // 1 -> 2 -> 3 -> null
        list2.last(3).print(); // 3 -> 4 -> 5 -> null

        empty.print(); // null
        list1.print(); // 1 -> 2 -> 3 -> null
        list2.print(); // 1 -> 2 -> 3 -> 4 -> 5 -> null
    }
}