using System;

using System.Collections.Generic;

using System.Diagnostics;

using System.Linq;

public class Program {

    public void Main() {

        int digits = 2;//6;

        int sum = 8;//10;

​

        bool verifyResults = true;

​

        RunSolution(Solution1, digits, sum, verifyResults);

    }

​

    void RunSolution(Func<int, int, bool, (int, List<long>)> solution, int digits, int sum, bool verifyResults) {

        if (sum > digits * 9) {

            throw new InvalidOperationException("The value of sum is too high for the number of digits.");

        }

​

        Stopwatch stopWatch = new Stopwatch();

        stopWatch.Start();

        (var count, var results) = solution(digits, sum, verifyResults);

        stopWatch.Stop();

​

        Console.WriteLine($"Found {count} results in {stopWatch.Elapsed}");

        results.ForEach(i=>Console.WriteLine("{0}\t",i));

​

        //String.Join(", ", results).Dump();

​

        //if (verifyResults && results.Any(r => SumOfDigits(r) != sum)) {

          //  Console.WriteLine("One or more results are wrong.");

        //}

    }

​

    // Solution 1

    (int count, List<long> results) Solution1(int digits, int sum, bool returnResults) {

        var count = 0;

        var results = new List<long>();

​

        // *** Include solution here ***

        //find number range for input # of digits

        int begin = (int) Math.Pow(10, digits - 1);

        int end = (int)Math.Pow(10, digits)-1;  

        int currentNum = begin;

        //loop through the range

        while(currentNum < end){

            int digitSum = 0;

            int digitCounter = currentNum;

            //find sum of digits in current number

            while(digitCounter != 0){

                digitSum += digitCounter % 10;

                digitCounter = digitCounter /10;

            }

            //if sum matches a number is found, increment current by 9 to get next possible match  

            if(digitSum == sum){

                count++;

                results.Add(currentNum);

                currentNum +=9;

            }

            else{

                currentNum++;

            }

        }

        return (count, results);

    }

}