Divide by 2 and round up in C without libraries [duplicate]-CodePudding

I need to know the price of all the offices that a company hires, knowing that you pay per office and there can be room for two workers per room, the problem is that I cannot use libraries or if...

monthlyPrice = oficePrice * (workers/2);
monthlyPrice = 100 * (7 / 2) = 350$

I need to either round up or find me another mathematical formula.

it could be done with a realtointegrer, i don´t now... :(

Thanks. Pablo.

CodePudding user response：

The simpliest way to round a floating point number x is as follows:

return (int)(x   0.5);

CodePudding user response：

I would suggest that you use the / and % operators.

/ will give you the integer section (left side of decimal point) for a division operation.

% will give you the remainder section (right side of the decimal point) of a division operation.

e.g. 7/2 gives 3

7%2 gives 1

You can then decide whether you wish to round up the result depending on the value returned by using %.

Ah I see that you're not allowed to use the if ... else ... construct. What about ... ? ... : ...?

CodePudding user response：

For money I would use fixed point.

//one cent is minimum we care
#define MULT    (100)  

#define MAKE_FIXED(d)  ((int32_t)(d * MULT))
#define MAKE_REAL(f)   (((double)(f)) / MULT)

int32_t mulf(int32_t a, int32_t b)
{
    int64_t part = (int64_t)a * b;
    return part/MULT;
}

int32_t divf(int32_t a, int32_t b)
{
    int64_t part = ((int64_t)a * MULT) / b;
    return part;
}


int main(void)
{
    int32_t officeprice = MAKE_FIXED(100);
    int32_t workers = MAKE_FIXED(7);

    
    printf("%f\n", MAKE_REAL(mulf(officeprice, divf(workers,MAKE_FIXED(2)))));

}