Question

I know that maybe its a silly question but I have some troubles with it, I’m ashamed but I really don’t know, how to make it. I want to add and subtract two ‘hours’ given as integers.

#include <iostream>
#include <cstdlib>
#include <cmath>
using namespace std;

int main()
{
    // should be: 21:59:2
    int rH, rM, rS;

    int h1 = 12, m1 = 34, s1 = 56;
    int h2 = 9, m2 = 24, s2 = 6;

    if(h1 + h2 >= 24)
    {
        rH = abs(h2 + h1);
        m1 += 60;

        if(m1 + m2 >= 60)
        {
            rH = (m2 - m1);
        }

    }
    else
    {
        rH = h1 + h2;
    }

    cout << rH << " " << rM << " " << rS << " " << "\n";

    return 0;
}

Tried the above but I don’t know how to do it further. I cant use any date-time objects.

EDIT

subtraction, I don’t know where the error is but it calculates wrong:

#include <iostream>
#include <cstdlib>
#include <cmath>
using namespace std;

int main()
{
    int rH, rM, rS;
    int h1 = 12, m1 = 25, s1 = 29, h2 = 11, m2 = 12, s2 = 1;
    int sum1, sum2, sum;

    sum1 = (h1)*3600 + (m1)*60 + s1;
    sum2 = (h2)*3600 + (m2)*60 + s2;

    if(sum1 > sum2)
        sum = sum1-sum2;
    else
        sum = sum2-sum1;

    rS = sum %60;
    sum = sum/60;
    rM = sum % 60;
    rH = sum/60;

    std::cout << rH << " " << rM << " " << rS << " " << "\n";

    return 0;
}

Answer 1

// addition
int rH=0, rM=0, rS=0; 

rS = s1+s2;
if (rS>60)
{
    rM++;
    rS %= 60;
}

rM += m1+m2;
if (rM>60)
{
    rH++;
    rM %= 60;
}

rH += h1+h2;
if (rH>24)
{
    // 1 day more, who cares
    rH %= 24;
}

cout << rH << " " << rM << " " << rS << " " << "\n";

---

// substraction

int rH = 0, rM = 0, rS = 0;
int h1 = 12, m1 = 25, s1 = 29, h2 = 11, m2 = 12, s2 = 1;

rS = s1 - s2;
if (rS<0)
{
    rM--;
    rS += 60;
}

rM += m1 - m2;
if (rM<0)
{
    rH--;
    rM += 60;
}

rH += h1 - h2;
if (rH<0)
{
    // Error occurred ...
}

cout << rH << " " << rM << " " << rS << " " << "\n";