using System;

public class Program

{

    public static void Main()

    {

            //After sorting the array (nlogn)

            int[] array = { 0, 1, 2, 3, 4, 5, 6, 7 };

            Program p = new Program();

            p.SumsofThree(array, 7);

    }

    public void SumsofThree(int[] arr, int sum)

        {

            int secIndex, lastIndex;

​

            for (int i = 0; i < arr.Length-2 ; i++)

            {

                secIndex = i + 1;

                lastIndex = arr.Length - 1;

                while (secIndex < lastIndex)

                {

                    int sum_three = arr[i] + arr[secIndex] + arr[lastIndex];

                    if (sum_three == sum)

                    {

                        Console.WriteLine(arr[i] + " " + arr[secIndex] + " " + arr[lastIndex] + " = " + sum);

                        lastIndex--;

                        secIndex++;

                    }

                    else if (sum_three < sum)

                        secIndex++;

                    else

                        lastIndex--;

                }

            }

        }

}