欧拉线性筛质数（线性）

#include<cstdio>#include<algorithm>#include<vector>#define maxn 10000005using namespace std;long long n;int siz;bool vis[maxn]={};vector<int>prime;int main(){scanf("%lld",&n);for(int i=2;i<=n;i++){if(!vis[i]) prime.push_back(i),siz++;for(int j=0;j<siz && i*prime[j]<=n;j++){vis[i*prime[j]]=1;if(i%prime[j]==0) break;}}bool flag=0;for(int i=0;i<siz;i++){if(flag) printf("*");else flag=1;printf("%d",prime[i]);}}