/*

Problem 20: Factorial digit sum

n! means n × (n − 1) × ... × 3 × 2 × 1

For example, 10! = 10 × 9 × ... × 3 × 2 × 1 = 3628800,

and the sum of the digits in the number 10! is 3 + 6 + 2 + 8 + 8 + 0 + 0 = 27.

Find the sum of the digits in the number 100!

*/

import 'package:test/test.dart';

// To Calculate Factorial

int factorial(int number) {

int factorial = 1;

for (int i = number; i >= 1; i--) {

factorial *= i;

}

return factorial;

}

// To Calculate Sum

int sum(int number) {

int sum = 0;

for (int i = factorial(number); i > 0; i = (i / 10).floor()) {

sum += (i % 10);

}

return sum;

}

// Driver Code

void main() {

group("Solution 20", () {

test("Test 1", () {

expect(1, sum(1));

});

test("Test 2", () {

expect(3, sum(5));

});

test("Test 3", () {

expect(27, sum(10));

});

});

}