patterncsharpMinor

Calculating solutions for the game "24"

Submitted by: @import:stackexchange-codereview·Mar 10, 2026·

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thecalculatingsolutionsgamefor

Problem

I was bored this evening and decided to create a program which calculates all the solutions for a given scenario of the game "24".

The goal of this game is that you try to be the first one to find the answer to a certain card. On the card are four numbers ranging from 1 to 9. The player is allowed to use subtract, add, multiply and divide to reach the number 24 and must use each number only once.

Example: 8,8,5,1 could result in 8-5 = 3, 31 = 3, 3 8 = 24.

I have put the operators into an enum and the selected numbers are put in a list in the beginning of the method. The following code calculates the solution correctly and in the end selects the unique solutions and puts that into a public property which is displayed.

The method to rule them all:

```
private void CalculateSolutions()
{
Solutions.Clear();
var numbers = new List(4) { NumberOne, NumberTwo, NumberThree, NumberFour };
var solutions = new List();

foreach (Operator operatorOne in Enum.GetValues(typeof (Operator)))
{
foreach (Operator operatorTwo in Enum.GetValues(typeof (Operator)))
{
foreach (Operator operatorThree in Enum.GetValues(typeof (Operator)))
{
for (var numberOneCounter = 0; numberOneCounter < numbers.Count; numberOneCounter++)
{
var numberOne = numbers[numberOneCounter];
for (var numberTwoCounter = 0; numberTwoCounter < numbers.Count; numberTwoCounter++)
{
if (numberTwoCounter == numberOneCounter)
continue;

var numberTwo = numbers[numberTwoCounter];
for (var numberThreeCounter = 0;
numberThreeCounter < numbers.Count;
numberThreeCounter++)
{
i

Solution

First of all implement Equals in your OperatorResult

public override bool Equals(object obj)
{
    return Equals(obj as OperatorResult);
}

public bool Equals(OperatorResult operatorResult)
{
    return operatorResult != null && 
           operatorResult.OperatorOne == this.OperatorOne && 
           operatorResult.OperatorTwo == this.OperatorTwo && 
           operatorResult.OperatorThree == this.OperatorThree && 
           operatorResult.NumberOne == this.NumberOne && 
           operatorResult.NumberTwo == this.NumberTwo && 
           operatorResult.NumberThree == this.NumberThree && 
           operatorResult.NumberFour == this.NumberFour;
}

public override int GetHashCode()
{
    var result = 0;
    result = (result * 397) ^ (int)OperatorOne;
    result = (result * 397) ^ (int)OperatorTwo;
    result = (result * 397) ^ (int)OperatorThree;
    result = (result * 397) ^ NumberOne;
    result = (result * 397) ^ NumberTwo;
    result = (result * 397) ^ NumberThree;
    result = (result * 397) ^ NumberFour;
    return result;
}

With it, you don't need the GetUniqueSolutions, you can just use Distinct.

Now, your code can be represented as this linq query:

void CalculateSolutions()
{
    var numbers = new List(4) { 8, 8, 5, 1 };

    var solutions = 
       (from operatorOne in (IEnumerable)Enum.GetValues(typeof(Operator))
        from operatorTwo in (IEnumerable)Enum.GetValues(typeof(Operator))
        from operatorThree in (IEnumerable)Enum.GetValues(typeof(Operator))
        from numberOne in numbers
        from numberTwo in GetRemainingNumbers(numbers, numberOne)
        from numberThree in GetRemainingNumbers(numbers, numberOne, numberTwo)
        from numberFour in GetRemainingNumbers(numbers, numberOne, numberTwo, numberThree)
        where GetTotalSum(numberOne, numberTwo, numberThree, numberFour, 
                          operatorOne, operatorTwo, operatorThree) == 24
        select new OperatorResult
        { 
            OperatorOne = operatorOne,
            OperatorTwo = operatorTwo,
            OperatorThree = operatorThree,
            NumberOne = numberOne,
            NumberTwo = numberTwo,
            NumberThree = numberThree,
            NumberFour = numberFour,
        }).Distinct();
}

IEnumerable GetRemainingNumbers(IEnumerable numbers, params int[] usedNumbers)
{
    var result = numbers.ToList();
    foreach (var number in usedNumbers)
    {
        result.Remove(number);
    }
    return result;
}

Code Snippets

public override bool Equals(object obj)
{
    return Equals(obj as OperatorResult);
}

public bool Equals(OperatorResult operatorResult)
{
    return operatorResult != null && 
           operatorResult.OperatorOne == this.OperatorOne && 
           operatorResult.OperatorTwo == this.OperatorTwo && 
           operatorResult.OperatorThree == this.OperatorThree && 
           operatorResult.NumberOne == this.NumberOne && 
           operatorResult.NumberTwo == this.NumberTwo && 
           operatorResult.NumberThree == this.NumberThree && 
           operatorResult.NumberFour == this.NumberFour;
}

public override int GetHashCode()
{
    var result = 0;
    result = (result * 397) ^ (int)OperatorOne;
    result = (result * 397) ^ (int)OperatorTwo;
    result = (result * 397) ^ (int)OperatorThree;
    result = (result * 397) ^ NumberOne;
    result = (result * 397) ^ NumberTwo;
    result = (result * 397) ^ NumberThree;
    result = (result * 397) ^ NumberFour;
    return result;
}

void CalculateSolutions()
{
    var numbers = new List<int>(4) { 8, 8, 5, 1 };

    var solutions = 
       (from operatorOne in (IEnumerable<Operator>)Enum.GetValues(typeof(Operator))
        from operatorTwo in (IEnumerable<Operator>)Enum.GetValues(typeof(Operator))
        from operatorThree in (IEnumerable<Operator>)Enum.GetValues(typeof(Operator))
        from numberOne in numbers
        from numberTwo in GetRemainingNumbers(numbers, numberOne)
        from numberThree in GetRemainingNumbers(numbers, numberOne, numberTwo)
        from numberFour in GetRemainingNumbers(numbers, numberOne, numberTwo, numberThree)
        where GetTotalSum(numberOne, numberTwo, numberThree, numberFour, 
                          operatorOne, operatorTwo, operatorThree) == 24
        select new OperatorResult
        { 
            OperatorOne = operatorOne,
            OperatorTwo = operatorTwo,
            OperatorThree = operatorThree,
            NumberOne = numberOne,
            NumberTwo = numberTwo,
            NumberThree = numberThree,
            NumberFour = numberFour,
        }).Distinct();
}

IEnumerable<int> GetRemainingNumbers(IEnumerable<int> numbers, params int[] usedNumbers)
{
    var result = numbers.ToList();
    foreach (var number in usedNumbers)
    {
        result.Remove(number);
    }
    return result;
}

Context

StackExchange Code Review Q#83515, answer score: 4

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