TheAlgorithms/C-Sharp · error

cannot contain numbers less than or equal to zero

Error message

{nameof(coinsAsArray)} cannot contain numbers less than or equal to zero

What it means

ValidateCoinsArray rejects coin systems containing zero or negative denominations, since coin values must be positive integers for change-making to be meaningful. It throws InvalidOperationException naming the offending parameter coinsAsArray.

Solutions

1. Filter out non-positive values: coins.Where(c => c > 0) before calling.
2. Fix the data source that produced 0/negative denominations.
3. Add caller-side validation with a clear error message naming the bad entry.

Example fix

// before
var coins = ParseCoins(userInput); // may contain 0
solver.GenerateSingleCoinChanges(coins, amount);
// after
var coins = ParseCoins(userInput).Where(c => c > 0).Distinct().ToArray();
solver.GenerateSingleCoinChanges(coins, amount);

if (coins != null && coins.Any(c => c <= 0)) throw new ArgumentException("All coin values must be positive.", nameof(coins));

try { solver.GenerateSingleCoinChanges(coins, amount); }
catch (InvalidOperationException ex) { Console.Error.WriteLine($"Invalid coin values: {ex.Message}"); }

When it happens

Trigger: Calling GenerateSingleCoinChanges with coins such as [0, 1, 5] or [-1, 2, 5] — any element <= 0.

Common situations: Parsing denominations from user input or a file where an empty/0 default slipped in; integer parsing of malformed rows yielding negatives; uninitialized placeholder entries in the array.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• Coins array must contain coin 1
• Coins array cannot contain duplicates
• message
• key must be non-empty string
• k must be at least 1.

AI-assisted analysis of TheAlgorithms/C-Sharp@96e2905cab (2026-09-13). Data as JSON: /api/errors/667726b3a7a31749. Report an issue: GitHub.

Appendix: source

Thrown at Algorithms/Problems/DynamicProgramming/CoinChange/DynamicCoinChangeSolver.cs:158

        var coinsAsArray = coinsArray.ToArray();

        if (coinsAsArray.Length == 0)
        {
            throw new InvalidOperationException($"Coins array cannot be empty {nameof(coinsAsArray)}.");
        }

        var coinsContainOne = coinsAsArray.Any(x => x == 1);

        if (!coinsContainOne)
        {
            throw new InvalidOperationException($"Coins array must contain coin 1 {nameof(coinsAsArray)}.");
        }

        var containsNonPositive = coinsAsArray.Any(x => x <= 0);

        if (containsNonPositive)
        {
            throw new InvalidOperationException(
                $"{nameof(coinsAsArray)} cannot contain numbers less than or equal to zero");
        }

        var containsDuplicates = coinsAsArray.GroupBy(x => x).Any(g => g.Count() > 1);

        if (containsDuplicates)
        {
            throw new InvalidOperationException($"Coins array cannot contain duplicates {nameof(coinsAsArray)}.");
        }
    }
}

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