Question

I have a problem. I need to get two numbers and add them together in a way that one is the decimal point of the other. For example:

double number1 = 20;
double number2 = 142;

I need to add these numbers together to get 20.142. Is there a way to do this?

Thanks

Answer 1

bool negative = (number1 < 0.0);

if (negative)
    number1 = 0 - number1;
while (number2 >= 1.0)
    number2 = number2 / 10.0;

double finalnum = number1 + number2;
if (negative)
    finalnum = 0 - finalnum;

It’s quite simple. We first determine if number1 is negative, and if so, make it positive and set a boolean flag. Then we just keep dividing number2 by 10.0 until it is less than 1.0 (which means it’s now on the range [0, 1) assuming it’s positive). Then we just add the two numbers together and store it in finalnum, and if negative is true (YES), negate finalnum.

This solution could have also been solved using base-10 logarithms to determine the amount to divide number2 by, but that most likely will take longer.

You could also have solved this by turning those numbers into const char* or CFString (Objective-C) strings and then concatenate them followed by an interpretation of the resulting string as a double, but again, this will take longer.

There are two caveats to this code:

1. number1 and number2 must be integers (if number1 was, say, 1.5 and number2 was 25.7, finalnum would be 1.757)
2. number2 must be positive