0_count_of_2.c

/* ************************************************************************** */
/*                                                                            */
/*                                                        :::      ::::::::   */
/*   count_of_2.c                                       :+:      :+:    :+:   */
/*                                                    +:+ +:+         +:+     */
/*   By: qpeng <marvin@42.fr>                       +#+  +:+       +#+        */
/*                                                +#+#+#+#+#+   +#+           */
/*   Created: 2018/09/28 21:32:57 by qpeng             #+#    #+#             */
/*   Updated: 2018/09/28 21:41:04 by qpeng            ###   ########.fr       */
/*                                                                            */
/* ************************************************************************** */
/*
	Assignment name  : count_of_2
	Expected files   : count_of_2.c
	Allowed functions: None
	--------------------------------------------------------------------------------
	Implement a function which counts, for a given integer n, the number of 2s
	that appear in all the numbers between 0 and n (inclusive).
	Your function must be declared as follows:
	int    count_of_2(int n);
	If n <= 1, the function returns 0;
	Examples:
	input  = 25
	output =  9
	because there are 9 2s in (2, 12, 20, 21, 22, 23, 24 and 25)
	Note:
	the number 22 counts as 2 because it has two 2s, number 202 count as 2, number 22022 count as 4 etc

*/
int		count_twos(int num)
{
	int	count = 0;
	while (num)
	{
		if (2 == num % 10)
			count++;
		num /= 10;
	}
	return (count);
}

int	    count_of_2(int n)
{
	int count = 0, i = 2;
	while (i <= n)
	{
		count += count_twos(i);
		i++;
	}
	return (count);
}
/*
#include <stdio.h>
#include <stdlib.h>
int 	main(int ac, char **av)
{
	if (ac == 2)
		printf("%d\n", count_of_2(atoi(av[1])));
	return (0);
}
*/