Counting Digits

readme.md

#Counting Digits in C++

Theoretically, taking the ceiling of the base-10 logarithm of a number should give you the number of digits for that number, but watch for powers of 10. Does looping over the digits slow down the program? You can't tell without profiling it in practice.

count_digits.cpp

#include <cmath>
#include <iostream>
#include <iomanip>
#include <vector>
#include <stdint.h>

using namespace std;

size_t countDigitsLog(int number)
{
	return ceil(log10((float)number));
}

size_t countDigitsLoop(int number)
{
	size_t digits = 0;
	if (!number)
		return 1;
	
	number = abs(number);
	while (number)
	{
		number /= 10;
		++digits;
	}

	return digits;
}

int main()
{
	int ints[] = {10, 100, 1000, 4192, 10000};
  size_t count = sizeof(ints)/sizeof(ints[0]);

	for (int i = 0; i < count; ++i)
	{
		cout << "Log-based count for  " << setw(5) << ints[i] << " is: " << setw(5) << countDigitsLog(ints[i]) << endl;
		cout << "Loop-based count for " << setw(5) << ints[i] << " is: " << setw(5) << countDigitsLoop(ints[i]) << endl;
	}

	return 0;
}