primo.c

/**
License: Creative Comons
Author: Antonio Ribeiro Alves júnior
**/

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

int *primo(int v)
{
    int *k = (int*)malloc(sizeof(int)*v);    
    int *result;
    int cont = 2;
    int i, raiz, j;

    for(i=0; i<v; i++)
        k[i] = i;
    
    i=2;
    raiz = (int)sqrt((float)v); 
    
    while(i<=raiz)
    {
        j = i;
        if(k[j] != 0)
        {
            while(j <= v-1)
            {
                j+=i;
                if(j <= v) 
                    k[j]=0;
            }
        }
        i++;
    }

    cont = 0;
    for(i=0; i<=v; i++)
        if(k[i]!=0)
            cont++;

    result = (int*)malloc(sizeof(int)*(cont+1));
    result[0] = cont;
    
    cont = 1; 
    
    for(i=0; i<=v; i++)
        if(k[i]!=0)          
            result[cont++]=k[i];


    free(k);
    return result;
}

int main()
{
    int *a, i;

    a = (int*)primo(10000000);
    
    for(i=0; i<= a[0]; i++)
        printf("%i ",a[i]);
    printf("\n");

return 0;
}