public bool IsValid(NumberChain numberChain)
{
try
{
// Only seven numbers
if (numberChain.Length != 7)
return false;
var operators =
Operators.Matches(numberChain.ToString()).Cast<object>().Select(x => x.ToString()).ToList();
// Only 6 operators
if (operators.Count != 6) return false;
// All 4 operators should be used
var grouped = operators.GroupBy(x => x);
if (grouped.Count() != 4) return false;
// Maximum of 2 operators can be used twice
var groupedByCount = grouped.GroupBy(x => x.Count());
var countOfOperatorsUsedTwice = groupedByCount.FirstOrDefault(x => x.Key == 2)?.Count();
if (countOfOperatorsUsedTwice != 2)
return false;
// Validated
return true;
}
catch
{
return false;
}
}
public static bool IsValidOn(this ArithmeticOperation operation, NumberChain left, byte right)
{
return operation.IsValidOn(left.Result ?? left.Number, right);
}
public IEnumerable<NumberChain> GenerateChains(byte number, NumberChain previous)
{
return GetPossibleOperations()
.Where(x => x.IsValidOn(previous, number))
.Select(x => new NumberChain(number, previous, x));
}
