【C++】埃拉托色尼筛子表示一定范围内的素数

#include<iostream>using namespace std;int main(){const int max = 10000;int a = 0;cin >> a;int b[max];memset(b,0,max);for(int i = 0;i<a;i++){b[i] = i;}int p = 0;for(int j = 2;j<a;j++){p = j*j;while(p<a){b[p] = 0;p += j;}}for(int i = 2;i<a;i++){if(b[i]!=0)printf("%d",b[i]);}}