Cattle off the driving range net PAT - the number of prime numbers

Solution: it is a prime number screening

Topic address: https: //www.nowcoder.com/questionTerminal/e0fb49acb75f47e8b6fa2077d9071799

. 1  / * *
 2  * Copyright (C)
 . 3  * All Rights Reserved.
 . 4  * the Author: Ycute
 . 5  * a Date: 2019-10-29-19.45.37
 . 6  * the Description: screening methods find prime number
 . 7  * / 
. 8 #include <the iostream>
 . 9 #include <cstdio>
 10 #include <the cmath>
 . 11 #include <CString>
 12 is #include <algorithm>
 13 is  the using  namespace STD;
 14  
15  // determines whether the number is prime; 
16  BOOL F ( int  in ) {
 . 17      for ( int i=2;i<=sqrt(in);++i){
18         if(in%i==0)return false;
19     }
20     return true;
21 }
22 bool flag[200005]={0};//标记数组
23 int main(){
24     flag[1]=1;
25     int a,b;
26     scanf("%d %d",&a,&b);
27     for(int i=2;i<200005;++i){
28         if(flag[i]) continue;
29         if(i==2||f(i)){}
30         else{
31             flag[i]=1;
32         }
33             int t=2;
34             while(t*i<=b){
35                 flag[t*i]=1;
36                 ++t;
37             }
38     }
39     int num=1;
40     int i=0;
41     while(num<a){
42         if(!flag[++i]) ++num;
43     }
44     int tt=0;//以10来循环
45     while(num<=b){
46         if(!flag[++i]){
47             if(tt==9||num==b)printf("%d\n",i);
48             else printf("%d ", i);
49              ++ projects;
50              tt = (tt + 1 )% 10 ;
51          }
 52      }
 53      return  0 ;
54 }