How can I count the digits in an integer without a string cast?

Question

I fear there\'s a simple and obvious answer to this question. I need to determine how many digits wide a count of items is, so that I can pad each item number with the m

Answer 1

int length = (int)Math.Log10(Math.Abs(number)) + 1;

You may need to account for the negative sign..

Answer 2

Okay, I can't resist: use /=:

#include <stdio.h>

int
main(){
        int num = 423;
        int count = 1;
        while( num /= 10)
                count ++;
        printf("Count: %d\n", count);
        return 0;
}
534 $ gcc count.c && ./a.out
Count: 3
535 $ 

Answer 3

You can loop through and delete by 10, count the number of times you loop;

int num = 423;
int minimum = 1;
while (num > 10) {
    num = num/10;
    minimum++;
}

Answer 4

You can use a while loop, which will likely be faster than a logarithm because this uses integer arithmetic only:

int len = 0;
while (n > 0) {
    len++;
    n /= 10;
}

I leave it as an exercise for the reader to adjust this algorithm to handle zero and negative numbers.