Question

I am working on Project Euler, the first problem, and I’ve gotten this program to output the numbers I need, but I cannot figure out how to take the outputted numbers and add them together.

Here’s the code:

#include <iostream>
#include <cmath>

int main(void) {

    int test = 0;

    while (test<1000) {
        test++;
            if (test%3 == 0 && test%5 == 0) {

                std::cout << test << std::endl;

            }
    }

    std::cin.get();

    return 0;
}

Answer 1

The easiest option would be a total variable that you add to as the criteria match.

The first step is creating it and initializing it to 0, so you end up with the right number later.

int total = 0;

After that, subtotals are added to it, so that it accumulates the overall total.

total += 5;
...
total += 2;
//the two subtotals result in total being 7; no intermediate printing needed

Once you’ve added on the subtotals, you can just print it as the overall total.

std::cout << total;

Now, here’s how it fits into the code at hand, along with some other pointers:

#include <iostream>
#include <cmath> //<-- you're not using anything in here, so get rid of it

int main() {
    int test = 0;
    int total = 0; //step 1; don't forget to initialize it to 0

    while (test<1000) { //consider a for loop instead
        test++;

        if (test % 3 == 0 && test % 5 == 0) {
            //std::cout << test << std::endl;
            total += test; //step 2; replace above with this to add subtotals
        }
    }

    std::cout << total << std::endl; //step 3; now we just output the grand total

    std::cin.get();    
    return 0; //this is implicit in c++ if not provided
}