using System;

using System.Collections.Generic;

using System.Linq;

namespace Interview

{

    public static class Utility

    {

        public static bool ContainsDuplicatesComplex(IEnumerable<int> data)

        {

             HashSet<int> myHash = new HashSet<int>();

​

            foreach (int i in data)

            {

                if (myHash.Contains(i))

                {                    

                    return true;

                }

                else

                {

                    myHash.Add(i);

                }

            }

            return false;

        }

        public static bool ContainsDuplicates(IEnumerable<int> data)

        {

            // TODO: Given a collection of integers, return:

            //   True if any integer is in the collection more than once

            //   False if all integers are unique.

             if (data.Count() != data.Distinct().Count())

                return true;

            else                            

                return false;

        }

    }

    public static class Program

    {

        public static void Main()

        {

            // TODO: Implement a few tests of the function ContainsDuplicates here.

             List<int> dups = new List<int>();

                dups.Add(1);

                dups.Add(2);

                dups.Add(2);

                dups.Add(3);

            //linq implementation

            var hasDuplicates = Utility.ContainsDuplicates(dups);

            Console.WriteLine(hasDuplicates);

            //hashset implementation

            hasDuplicates = Utility.ContainsDuplicatesComplex(dups);

            Console.WriteLine(hasDuplicates);

        }       

    }

}