wangzhao 筛选求解素数

#include <stdio.h>
#include <math.h>
#define N 100000
int main()
{
int m,doub;
int n=0,num,i;
int a
;
scanf("%d",&num);
for(i=2; i<=num; i++)
a[i]=1;
m=2;
double k;
k=sqrt(num);
while(m<k+1)
{
doub=2*m;
while(doub<=num)
{
a[doub]=0;
doub+=m;
}
do
{
m++;

}
while(a[m]==0);
}
for(i=2; i<=num; i++)
if(a[i]==1)
{
printf("   %2d",i);
n++;
if(n%10==0)
printf("\n");
}
printf("\n");
return 0;
}