count_of_trailing_ciphers_in_factorial_n.cpp

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#include <cassert>   
#include <cstdint>
#include <iostream>  
 
namespace bit_manipulation {
namespace count_of_trailing_ciphers_in_factorial_n {
uint64_t numberOfCiphersInFactorialN(uint64_t n) {
    // count is to store the number of 5's in factorial(n)
    uint64_t count = 0;
 
    // Keep dividing n by powers of
    // 5 and update count
    for (uint64_t i = 5; n / i >= 1; i *= 5) {
        count += static_cast<uint64_t>(n) / i;
    }
 
    return count;
}
}  // namespace count_of_trailing_ciphers_in_factorial_n
}  // namespace bit_manipulation
 
static void test() {
    // 1st test
    std::cout << "1st test ";
    assert(bit_manipulation::count_of_trailing_ciphers_in_factorial_n::
               numberOfCiphersInFactorialN(395) == 97);
    std::cout << "passed" << std::endl;
 
    // 2nd test
    std::cout << "2nd test ";
    assert(bit_manipulation::count_of_trailing_ciphers_in_factorial_n::
               numberOfCiphersInFactorialN(977) == 242);
    std::cout << "passed" << std::endl;
 
    // 3rd test
    std::cout << "3rd test ";
    assert(bit_manipulation::count_of_trailing_ciphers_in_factorial_n::
               numberOfCiphersInFactorialN(871) == 215);
    std::cout << "passed" << std::endl;
 
    // 4th test
    std::cout << "4th test ";
    assert(bit_manipulation::count_of_trailing_ciphers_in_factorial_n::
               numberOfCiphersInFactorialN(239) == 57);
    std::cout << "passed" << std::endl;
 
    // 5th test
    std::cout << "5th test ";
    assert(bit_manipulation::count_of_trailing_ciphers_in_factorial_n::
               numberOfCiphersInFactorialN(0) == 0);
    std::cout << "passed" << std::endl;
}
 
int main() {
    test();  // run self-test implementations
    return 0;
}