COJ 2024 仙境传奇（五）——一个天才的觉醒 素数筛

#include<iostream>
#include<cstdio>
#include<cmath>
#include<algorithm>
#include<queue>
#include<cstring>
#define PAU putchar(' ')
#define ENT putchar('\n')
using namespace std;
const int maxn=10000000+10;
bool pri[maxn];
void makepri(int n){
int lim=sqrt(n);memset(pri,true,sizeof(pri));
for(int i=2;i<=lim;i++)if(pri[i])for(int j=i*i;j<=n;j+=i)pri[j]=false;return;
}
inline int read(){
int x=0,sig=1;char ch=getchar();
while(!isdigit(ch)){if(ch=='-')sig=-1;ch=getchar();}
while(isdigit(ch))x=10*x+ch-'0',ch=getchar();
return x*=sig;
}
inline void write(int x){
if(x==0){putchar('0');return;}if(x<0)putchar('-'),x=-x;
int len=0,buf[15];while(x)buf[len++]=x%10,x/=10;
for(int i=len-1;i>=0;i--)putchar(buf[i]+'0');return;
}
int n;
void init(){
n=read();makepri(n);
for(int i=2;i<=n;i++) if(pri[i]) write(i),ENT;
return;
}
void work(){
return;
}
void print(){
return;
}
int main(){init();work();print();return 0;}