code/prime-sieve/sieve.c

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <inttypes.h>


#define NON_PRIME 1
#define PRIME 2

typedef struct value {
    long long number;
    uint8_t flag;
} value;

int main (int argc, char** argv) {
    if (argc != 2) {
        printf("usage: %s [upper limit]", argv[0]);
        return -1;
    }
    long long limit = atoll(argv[1]);
    value *v;
    v = malloc(sizeof(value) * limit);

    // fill value
    for (int i = 2;  i < limit - 2; ++i){
        v[i].number = i;
        v[i].flag = 0;
    }


    for (long long i = 2;  i < limit - 2; ++i){
        if (v[i].flag == NON_PRIME) {
            continue;
        }
        v[i].flag = PRIME;
        long long z = i;
        long long j = z * z;
        while (j < limit) {
            v[j].flag = NON_PRIME;
            j = v[i].number * z;
            z++;
        }
    }
    long long count = 0;
    for (long long i = 2;  i < limit - 2; ++i){
         if (v[i].flag == PRIME) {
             printf("\nPrime: %lld", v[i].number);
             count ++;
         }
     }

     printf("\n\nTotal Primes: %lld", count);

     return 0;
}