using System;

using System.Linq;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        var array1 = new int[] { 1, 2, 3, 4 }

​

        ;

        var array2 = new int[] {353, 588, 213, 353}

​

        ;

        var dic = new Dictionary<int, int>();

        for (int i = 0; i < array2.Length; i++)

        {

            int index = array2[i];

            if (dic.ContainsKey(index))

            {

                dic[index] += array1[i];

            }

            else

            {

                dic.Add(index, array1[i]);

            }

        }

​

        array1 = new int[dic.Count];

        array2 = new int[dic.Count];

        int position = 0;

        foreach (var kvp in dic)

        {

            array1[position] = kvp.Value;

            array2[position] = kvp.Key;

            position++;

        }

        Console.WriteLine(String.Join(", ", array1));       

        Console.WriteLine(String.Join(", ", array2));

    }

}