Question

How to sum the digit of a factorial of a number in C#

Answer 1

using System;

class FactorialAndSumDigits
{
    static int SumDigits(long num) {
        int sum = 0;
        
        while (num != 0) {
            sum += (int)(num % 10);
            num /= 10;
        }
        
        return sum;
    }

    static long Factorial(long n) {
        return (n == 1 || n == 0) ? 1 : n * Factorial(n - 1);
    }

    static void Main()
    {
        long number = 9;
        long result = Factorial(number);

        Console.WriteLine("factorial = " + result);
        Console.WriteLine("sum digits = " + SumDigits(result));
    }
}


  
/*
run:
  
factorial = 362880
sum digits = 27
  
*/

 

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