C语言程序 输出所有小于n的素数（n >=2）
1、ubuntu 14.04 linux c
gcc (Ubuntu 4.8.2-19ubuntu1) 4.8.2
2、#include<stdio.h>
#include <stdlib.h>
int main()
{
int *primes_array = NULL;
int num = 0,i = 0,j = 0,index = 0,flag = 0;
printf("please enter a num (2 <= n <= 100000) :\n");
scanf("%d",&num);
if(num < 2){
printf("too small !!\n");
return 0;
}
if(num > 100000){
printf("too larger !!\n");
return 0;
}
primes_array =(int *)malloc(num*sizeof(int));
for(i=0;i<num;i++)
primes_array[i] = 0;
primes_array[0] = 2;
index = 0;
for(i=2;i<=num;i++)
{
for(j=0;j<=index;j++){
flag = i % primes_array[j];
if(flag == 0)
break;
}
if(flag){
index ++;
primes_array[index] = i;
}
}
printf("the prime nums are (n < %d ):\n",num);
for(i=0;i<=index;i++)
{
printf("%d,\n",primes_array[i]);
}
free(primes_array);
return 0;
}
3、xxx@linux:~/code# gcc -o primes primes.c
xxx@linux:~/code# ./primes
please enter a num (2 <= n <= 100000) :
13
the prime nums are (n < 13 ):
2,
3,
5,
7,
11,
13,
xxx@linux:~/code# ./primes
please enter a num (2 <= n <= 100000) :
5
the prime nums are (n < 5 ):
2,
3,
5,