HDU2138How many prime numbers

Posted 2020-08-17 chty

【题目大意】

给n个数判断有几个素数。（每个数<=2^32）

注意多组数据

 

【题解】

用Rabin_Miller测试跑得飞快。。。

 1 /*************
 2   HDU 2138
 3   by chty
 4   2016.11.5
 5 *************/
 6 #include<iostream>
 7 #include<cstdio>
 8 #include<cstring>
 9 #include<cstdlib>
10 #include<ctime>
11 #include<cmath>
12 #include<algorithm>
13 using namespace std;
14 typedef long long ll;
15 ll n,ans;
16 inline ll read()
17 {
18     ll x=0,f=1;  char ch=getchar();
19     while(!isdigit(ch))  {if(ch==‘-‘)  f=-1;  ch=getchar();}
20     while(isdigit(ch))  {x=x*10+ch-‘0‘;  ch=getchar();}
21     return x*f;
22 }
23 ll fast(ll a,ll b,ll mod) {ll sum=1;for(;b;b>>=1,a=a*a%mod)if(b&1)sum=sum*a%mod;return sum;}//一行快速幂
24 bool Rabin_Miller(ll p,ll a)
25 {
26     if(p==2)  return 1;
27     if(p&1==0||p==1)  return 0;
28     ll d=p-1;
29     while(!(d&1))  d>>=1;
30     ll m=fast(a,d,p);
31     if(m==1)  return 1;
32     while(d<p)
33     {
34         if(m==p-1)  return 1;
35         d<<=1;
36         m=m*m%p;
37     }
38     return 0;
39 }
40 bool isprime(ll x)
41 {
42     static ll prime[9]={2,3,5,7,11,13,17,19,23};
43     for(ll i=0;i<9;i++)
44     {
45         if(x==prime[i])  return 1;
46         if(!Rabin_Miller(x,prime[i]))  return 0;
47     }
48     return 1;
49 }
50 int main()
51 {
52     freopen("cin.in","r",stdin);
53     freopen("cout.out","w",stdout);
54     while(~scanf("%lld",&n))
55     {
56         ans=0;
57         for(ll i=1;i<=n;i++)  
58         {
59             ll x=read();
60             if(isprime(x))  ans++;
61         }
62         printf("%lld\n",ans);
63     }
64     return 0;
65 }