Calculate Factorial various languages

C#

• Classic recursive

public static int CalculateFactorialRecursive(int number)
{
	return number == 0 ? 1 : number * CalculateFactorialRecursive(number - 1);
}

• Iterative

public static int CalculateFactorial(int number)
{
	return number == 0 ? 1 : Enumerable.Range(1, number).Aggregate(1, (current, i) => current * i);
}

Python

def calculate_factorial(input_number: int, recursive: bool = False) -> int | None:
    if input_number == 0:
        return 1
    if recursive:
        return input_number * calculate_factorial(input_number - 1, True)

    result = input_number
    while input_number > 1:
        result *= input_number - 1
        input_number -= 1
    return result

Combines the two above to do both options by passing optional field of recursive boolean

JavaScript

JavaScript will do tail call optimization for this making it more efficient

function calculate_factorial(input_number, recursive) {
    if (input_number === 0) {
        return 1;
	}
    if (recursive) {
		return input_number * calculate_factorial(input_number - 1, true)
	}        

    result = input_number
    while (input_number > 1) {
        result *= input_number - 1
        input_number -= 1	
	}
    return result;
}