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I used this question Find out which combinations of numbers in a set add up to a given total which uses a C# example to attempt to find all the possible combinations of numbers which add up to a given number.

I used the code as provided and have attempted to understand it and I think I do, however, I can't figure out why this error is occurring.

Here is the setup:

public class Program
 
 public static void Main(string[] args)
 
 // subtotal list
 List<double> totals = new List<double>(new double[] 17.5, 14.3, 10.9, 7.8, 6.3, 3.8, 3.2, 2.7, 1.8, 1.0 );
 List<double> totals2 = new List<double>(new double[] 17.5, 14.3, 7.8, 6.3, 3.2, 1.8);

 // get matches
 List<double[]> results = Knapsack.MatchTotal(50.9, totals2);

 // print results`
 foreach (var result in results)
 
 Console.WriteLine(string.Join(",", result));
 

 Console.WriteLine("Done.");
 Console.ReadKey();
 

and the main bulk of the code is unchanged from the example.

public class Knapsack
 
 internal static List<double[]> MatchTotal(double theTotal, List<double> subTotals)
 
 List<double[]> results = new List<double[]>();

 while (subTotals.Contains(theTotal))
 
 results.Add(new double[1] theTotal );
 subTotals.Remove(theTotal);
 

 // if no subtotals were passed
 // or all matched the Total
 // return
 if (subTotals.Count == 0)
 return results;

 subTotals.Sort();

 double mostNegativeNumber = subTotals[0];
 if (mostNegativeNumber > 0)
 mostNegativeNumber = 0;

 // if there aren't any negative values
 // we can remove any values bigger than the total
 if (mostNegativeNumber == 0)
 subTotals.RemoveAll(d => d > theTotal);

 // if there aren't any negative values
 // and sum is less than the total no need to look further
 if (mostNegativeNumber == 0 && subTotals.Sum() < theTotal)
 return results;

 // get the combinations for the remaining subTotals
 // skip 1 since we already removed subTotals that match
 for (int choose = 2; choose <= subTotals.Count; choose++)
 
 // get combinations for each length
 IEnumerable<IEnumerable<double>> combos = Combination.Combinations(subTotals.AsEnumerable(), choose);

 // add combinations where the sum mathces the total to the result list
 results.AddRange(from combo in combos
 where combo.Sum() == theTotal
 select combo.ToArray());
 

 return results;
 


public static class Combination

 public static IEnumerable<IEnumerable<T>> Combinations<T>(this IEnumerable<T> elements, int choose)
 
 return choose == 0 ? // if choose = 0
 new[] new T[0] : // return empty Type array
 elements.SelectMany((element, i) => // else recursively iterate over array to create combinations
 elements.Skip(i + 1).Combinations(choose - 1).Select(combo => (new[] element ).Concat(combo)));
 

I have provided the set of numbers which is in totals which are used to try and calculate the total.

I entered 50.9 as the total and return no results.

The second set of numbers totals2 is a set of numbers which add up to 50.9 and they are a subset of totals. This also fails to return a result for 50.9
For some reason the code is unable to find 50.9 in the master set or in the subset (which itself sums to 50.9).

I can't figure out why it does this, can anyone tell me?