C++ factorial function not working - c++

Question

Can someone please help me understand why this code isn't working properly? I know it's very close and I think that I'm just overlooking something. Any help is appreciated. Here is what I have so far:
#include <iostream>
#define TEST_ARRAY_SIZE 4
long int factorial(int num);
long int factorial(int num){
for(unsigned int i = 1; i <= num; i++) {
num *= i;
}
return num;
}
int main() {
int test[TEST_ARRAY_SIZE] = {1, 2, 5, 7};
for (unsigned int i = 0; i < TEST_ARRAY_SIZE; i++) {
std::cout << "Factorial of " << test[i] << " is " << factorial(test[i]) << std::endl;
}
return 0;
}

Answer 1

You should move return num; outside the loop. As it is now, control always return after the first number is multiplied.
-- the correct code --
long int factorial(int num){
long int res = 1;
for(unsigned int i = 1; i <= num; i++) {
res *= i;
}
return res;
}

Answer 2

The body of the factorial function is not correct. You can use a recursive method to compute the factorial of a specific number. The corrected program of your version is below:
#include <iostream>
#define TEST_ARRAY_SIZE 4
long int factorial(int num);
int main() {
int test[TEST_ARRAY_SIZE] = {1, 2, 5, 7};
for (unsigned int i = 0; i < TEST_ARRAY_SIZE; i++) {
std::cout << "Factorial of " << test[i] << " is " << factorial(test[i]) << std::endl;
}
return 0;
}
long int factorial(int num){
if (num == 1)
return num;
else
return num * factorial(num-1);
}

Answer 3

That's only part of the problem; it's a case in which proper indentation would make the bug apparent in an instant.
In addition to that, why are you using num inside the loop? You should leave it as-is and declare a new variable to compound and return the result.
long int factorial(unsigned int num) {
int x = 1;
for(unsigned int i = 1; i <= num; i++) {
x *= i;
}
return x;
}
Other things to note:
You shouldn't be using a #define; you should declare a const instead.
You're comparing an unsigned against a signed in the factorial() for loop.