Euler 10

euler10.c

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

typedef unsigned long ul;

ul *maxprimeslist(ul max, int *found) {
    int cprimes = 10;
    ul *primes = (ul *)malloc(cprimes * sizeof(ul));
    int nprimes = 0;
    
    int i, j, prime;
    for (i = 2; i < max; ++i) {
        prime = 1;
        ul max = (ul)sqrt((double)i);
        for (j = 0; j < nprimes; ++j) {
            if (max < primes[j])
                break;
            if (i % primes[j] == 0) {
                prime = 0;
                break;
            }
            
        }
        if (prime) {
            ++nprimes;
            if (nprimes >= cprimes) {
                cprimes *= cprimes;
                primes = (ul *)realloc(primes, cprimes * sizeof(ul));
            }
            primes[nprimes - 1] = i;
        }
    }
    *found = nprimes;
    return primes;
}

int main(int argc, char **argv) {
    if (argc != 2) {
        printf("Wrong!\n");
        return 1;
    }
    ul n = strtoul(argv[1], NULL, 0);
    int found;
    ul *primes = maxprimeslist(n, &found);
    ul sum = 0;
    ul i;
    for (i = 0; i < found; ++i) {
        sum += primes[i];
    }
    free(primes);
    printf("Sum: %lu\n", sum);
    return 0;
}