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请教，这道题目是不是应该用筛选法~~~？请高手指点啊！不过我用筛选，得到的结果是错的，找不出问题出在哪里。
#include <iostream>
#include <cmath>
using namespace std;
int main(void)
{
unsigned int H;
unsigned long i,j,index;
unsigned int count;
int *a=new int[1000002];
for(i=1;i<1000002;i++)a[i]=1;
for(i=5;i<1000002;i+=4){
for(j=5,index=i*j;index<1000002,j<(1000002/i)+1;j+=4)
{
index=i*j;
a[index]=0;
}
}
while(1){
cin>>H;
if(H ==0)
break;
count=0;
for(i=5;i<=H;i+=4){
if(a[i])
count++;
}
cout<<H<<" "<<count<<endl;
}
delete[]a;
return 0;
}
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