using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        /*

        You run an e-commerce website and want to record the last N order ids in a log. Implement a data structure to accomplish this, with the following API:

​

        record(order_id): adds the order_id to the log

        get_last(i): gets the ith last element from the log. i is guaranteed to be smaller than or equal to N.

        You should be as efficient with time and space as possible.

        */

        Console.WriteLine("Hello World");

        var logger = new Logger();

        logger.record("a1");

        logger.record("b2");

        logger.record("c3");

        logger.record("d4");

        logger.record("e5");

        logger.record("f6");

        logger.record("g7");

        Console.WriteLine(logger.get_last(1) + " should be g7");

        Console.WriteLine(logger.get_last(7) + " should be a1");

    }

}

​

public class Logger

{

    // YOLO

    private List<string> orderLog;

    public Logger()

    {

        orderLog = new List<string>();

    }

    public void record(string order_id)

    {

        // add order_id to the log

        orderLog.Add(order_id);

        // insert is log(N). https://referencesource.microsoft.com/#mscorlib/system/collections/generic/list.cs,eb66b6616c6fd4ef

        // if they want an INSERT and a LOOKUP of O(1), there needs to be an index on an hash table or something

    }

    public string get_last(int i)

    {

        // gets the ith last element from the log. i is guaranteed to be smaller than or equal to N.

        return orderLog[orderLog.Count - i];

    }

}