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

For any input other than 0, compute the base-10 logarithm of the absolute value of the input, take the floor of that result and add 1:

int dig;
...
if (input == 0)
  dig = 1;
else
  dig = (int) floor(log10(abs((double) input))) + 1;

0 is a special case and has to be handled separately.