public static long GetSolutionOfProblem34()
{
// An easy upper bound is 10 000 000, but the computation shows they are all below 50 000.
var upperBound = 50000;
var listOfNumbersThatCanBeWrittenAsSumOfFactorialsOfDigits =
Enumerable.Range(3, upperBound)
.Where(number => FactorialHelper.IsSumOfFactorialOfDigits(number));
return(listOfNumbersThatCanBeWrittenAsSumOfFactorialsOfDigits.Sum());
}
public static BigInteger NumberOfPermutations(string number)
{
var numberOfPermutations = FactorialHelper.Factorial(number.Length);
var distinctCharacters = number.Distinct();
foreach (char distinctCharacter in distinctCharacters)
{
var numberOfTimesInNumber = number.Where(character => character == distinctCharacter).Count();
numberOfPermutations /= FactorialHelper.Factorial(numberOfTimesInNumber);
}
return(numberOfPermutations);
}
public static long GetSolutionOfProblem53()
{
var max = 100;
return(FactorialHelper.NumberOfCombinatoricSelectionsExceedingOneMillion(max));
}
