COJ 2024 仙境传奇（五）——一个天才的觉醒 素数筛

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cmath>
 4 #include<algorithm>
 5 #include<queue>
 6 #include<cstring>
 7 #define PAU putchar(‘ ‘)
 8 #define ENT putchar(‘\n‘)
 9 using namespace std;
10 const int maxn=10000000+10;
11 bool pri[maxn];
12 void makepri(int n){
13     int lim=sqrt(n);memset(pri,true,sizeof(pri));
14     for(int i=2;i<=lim;i++)if(pri[i])for(int j=i*i;j<=n;j+=i)pri[j]=false;return;
15 }
16 inline int read(){
17     int x=0,sig=1;char ch=getchar();
18     while(!isdigit(ch)){if(ch==‘-‘)sig=-1;ch=getchar();}
19     while(isdigit(ch))x=10*x+ch-‘0‘,ch=getchar();
20     return x*=sig;
21 }
22 inline void write(int x){
23     if(x==0){putchar(‘0‘);return;}if(x<0)putchar(‘-‘),x=-x;
24     int len=0,buf[15];while(x)buf[len++]=x%10,x/=10;
25     for(int i=len-1;i>=0;i--)putchar(buf[i]+‘0‘);return;
26 }
27 int n;
28 void init(){
29     n=read();makepri(n);
30     for(int i=2;i<=n;i++) if(pri[i]) write(i),ENT;
31     return;
32 }
33 void work(){
34     return;
35 }
36 void print(){
37     return;
38 }
39 int main(){init();work();print();return 0;}