check_factorial.cpp

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#include <cassert>   
#include <cstdint>
#include <iostream>  
 
namespace math {
bool is_factorial(uint64_t n) {
    if (n <= 0) {  // factorial numbers are only ever positive Integers
        return false;
    }
 
    int i = 2;
    while (n % i == 0) {
        n = n / i;
        i++;
    }
 
    return (n == 1);
}
}  // namespace math
 
static void tests() {
    assert(math::is_factorial(50) == false);
    assert(math::is_factorial(720) == true);
    assert(math::is_factorial(0) == false);
    assert(math::is_factorial(1) == true);
    assert(math::is_factorial(479001600) == true);
    assert(math::is_factorial(-24) == false);
 
    std::cout << "All tests have successfully passed!" << std::endl;
}
 
int main() {
    tests();  // run self-test implementations
    return 0;
}