Get number of digits of a number

Question

I have a number like this: int num = 36729; and I want to get the number of digits that compose the number (in this case 5 digits).

How can I do this?

Answer 1

1. The number of digits of an integer n in any base is trivially obtained by dividing until you're done:

unsigned int number_of_digits = 0;
do {
    ++number_of_digits; 
    n /= base;
} while (n);

2. Not necessarily the most efficient, but one of the shortest and most readable using C++: std::to_string(num).length()

3. And there is a much better way to do it:

#include
...
int size = trunc(log10(num)) + 1
...