Adv2015/D24.1/Program.cs

using System;
using System.IO;
using System.Linq;

namespace D24._1
{
    class Program
    {
        static void Main(string[] args)
        {
            if (args.Length < 1) throw new ArgumentException();
            if (File.Exists(args[0]) == false) throw new FileNotFoundException();

            int[] presentsWeight = File.ReadAllLines(args[0]).Select(i => int.Parse(i)).ToArray();

            var sum = presentsWeight.Sum();

            var p1 = Test(presentsWeight, sum / 3);
            var p2 = Test(presentsWeight, sum / 4);

            Console.WriteLine($"The part1 answer is : {p1}");
            Console.WriteLine($"The part2 answer is : {p2}");
        }

        static double? Test(int[] presentsWeight, int weight, double quantumE = 1, int totalWeight = 0, int i = 0 )
        {
            if (totalWeight == weight)
                return quantumE;

            if (i >= presentsWeight.Length || totalWeight > weight)
                return null;

            var take = Test(presentsWeight, weight, quantumE * presentsWeight[i], totalWeight + presentsWeight[i], i + 1);

            var ignore = Test(presentsWeight, weight, quantumE, totalWeight, i + 1);

            if (take == null) return ignore;
            if (ignore == null) return take;

            return Math.Min(take.GetValueOrDefault(0), ignore.GetValueOrDefault(0));
        }
    }
}