iterative_factorial.cpp

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#include <cassert>    
#include <cstdint>    
#include <exception>  
#include <iostream>   

namespace math {

uint64_t iterativeFactorial(uint8_t n) {
    if (n > 20) {
        throw std::invalid_argument("Maximum n value is 20");
    }
 
    // 1 because it is the identity number of multiplication.
    uint64_t accumulator = 1;
 
    while (n > 1) {
        accumulator *= n;
        --n;
    }
 
    return accumulator;
}
 
}  // namespace math

static void test() {
    // Special case test
    std::cout << "Exception case test \n"
                 "Input: 0 \n"
                 "Expected output: 1 \n\n";
    assert(math::iterativeFactorial(0) == 1);
 
    // Base case
    std::cout << "Base case test \n"
                 "Input: 1 \n"
                 "Expected output: 1 \n\n";
    assert(math::iterativeFactorial(1) == 1);
 
    // Small case
    std::cout << "Small number case test \n"
                 "Input: 5 \n"
                 "Expected output: 120 \n\n";
    assert(math::iterativeFactorial(5) == 120);
 
    // Medium case
    std::cout << "Medium number case test \n"
                 "Input: 10 \n"
                 "Expected output: 3628800 \n\n";
    assert(math::iterativeFactorial(10) == 3628800);
 
    // Maximum case
    std::cout << "Maximum case test \n"
                 "Input: 20 \n"
                 "Expected output: 2432902008176640000\n\n";
    assert(math::iterativeFactorial(20) == 2432902008176640000);
 
    // Exception test
    std::cout << "Exception test \n"
                 "Input: 21 \n"
                 "Expected output: Exception thrown \n";
 
    bool wasExceptionThrown = false;
    try {
        math::iterativeFactorial(21);
    } catch (const std::invalid_argument&) {
        wasExceptionThrown = true;
    }
    assert(wasExceptionThrown);
 
    std::cout << "All tests have passed successfully.\n";
}

int main() {
    test();  // Run self-test implementation
    return 0;
}