C Implementation of Problem 3

View source code here on GitHub!

Includes

• "macros.h" (implicitly, via primes.h)

• "primes.h"

• "math.h" (implicitly, via primes.h & if compiled on PCC)

• <inttypes.h>

• <stdint.h>

• <stdio.h>

• <stdlib.h> (implicitly, via primes.h & if not compiled on PCC)

• <math.h> (implicitly, via primes.h & if not compiled on PCC)

• <stdbool.h> (implicitly, via primes.h)

Solution

uint16_t p0003()

int main(int argc, char const *argv[])

Note

This function is only present in the Python test runner, or when compiling as a standalone program. It is not present when compiling for the Unity test runner.

/*
Project Euler Problem 3

More lazy functions this time. Took a little while to figure out how to
eliminate the special case for 2.

Problem:

The prime factors of 13195 are 5, 7, 13 and 29.

What is the largest prime factor of the number 600851475143 ?
*/
#ifndef EULER_P0003
#define EULER_P0003
#include <stdint.h>
#include <inttypes.h>
#include <stdio.h>
#include "include/macros.h"
#include "include/primes.h"

uint16_t EMSCRIPTEN_KEEPALIVE p0003() {
    uint16_t answer = 0;
    prime_factor_counter pfc = prime_factors(600851475143);
    while (!pfc.exhausted)
        answer = next(pfc);
    free_prime_factor_counter(pfc);
    return answer;
}

PROGRAM_TAIL("%" PRIu16, p0003)
#endif

Tags: c-iterator, factorization, prime-number