fprime

Introduction

fprime is a simple algorithm that finds and prints all the prime factors of a given number. A prime factor is a number that is a prime number and divides the given number without leaving a remainder.

In order to find the prime factors of a number, we need to divide the number by the smallest prime number (2) and continue dividing the result by the smallest prime number until the result is 1.

Info

In this exercise we are allowed to use external functions: atoi() and printf(). This simplifies the task a lot.

For example:

$ ./a.out 42 | cat -e
2*3*7$

Code

#include <stdlib.h>
#include <stdio.h>
 
int main(int argc, char **argv) {
    if (argc == 2) {
        int divider = 2;
        int num = atoi(argv[1]);
 
        while (num > 1) {
            while (num % divider == 0) {
				printf("%d", divider);
                num = num / divider;
                if (num > 1)
                    printf("*");
            }
            divider++;
        }
    }
    printf("\n");
    return 0;
}