using System;

using System.Collections.Generic;

using System.Linq;

using System.Diagnostics;

​

using RandomNameGeneratorLibrary;

public class Program

{

    public static void Main()

    {

        var searchedIds = new List<int> { 1, 3, 5, 100, 23, 2, 44, 170, 999, 821, 300 };

        for (var i = 1000; i< 10000; i++) searchedIds.Add(i);

        var users = GenerateTestList().ToList();

        var sw = new Stopwatch();

        sw.Start();

        // TASK: Implement method functionality

        var filteredUsers = FindUsersById(users, searchedIds);

        sw.Stop();

        Console.WriteLine("Stopwatch: " + sw.Elapsed);

        Console.WriteLine(filteredUsers.Count());

    }

    // WRITE YOUR CODE HERE

    private static IEnumerable<User> FindUsersById(IEnumerable<User> list, IEnumerable<int> ids) 

    {

        return list.Where(x => ids.Contains(x.Id)).ToList();

    }

    // **************************************************************

    // NOT IN THE TEST SCOPE 

    // **************************************************************

    // This method is for the data mock and is not in the test scope.

    private static IEnumerable<User> GenerateTestList() {

        var personGenerator = new PersonNameGenerator();

        for (var i=0; i < 100000; i++) {

            var user = new User {

                Id = i,

                Name = personGenerator.GenerateRandomFirstAndLastName()

            };

            yield return user;

        }

    }

}

​

public class User {

    public int Id { get; set; }

    public string Name { get; set; }

}