2019杭电多校第三场 6608 Fansblog（威尔逊定理+miller

Problem Description
传送门
Farmer John keeps a website called ‘FansBlog’ .Everyday , there are many people visited this blog.One day, he find the visits has reached P , which is a prime number.He thinks it is a interesting fact.And he remembers that the visits had reached another prime number.He try to find out the largest prime number Q ( Q < P ) ,and get the answer of Q! Module P.But he is too busy to find out the answer. So he ask you for help. ( Q! is the product of all positive integers less than or equal to n: n! = n * (n-1) * (n-2) * (n-3) *… * 3 * 2 * 1 . For example, 4! = 4 * 3 * 2 * 1 = 24 )

Input
First line contains an number T(1<=T<=10) indicating the number of testcases.
Then T line follows, each contains a positive prime number P (1e9≤p≤1e14)

Output
For each testcase, output an integer representing the factorial of Q modulo P.

Sample Input
1
1000000007

Sample Output
328400734

#include<iostream>
#include<stdio.h>
#include<math.h>
#include<algorithm>
#include<string>
#include<cstring>
#include<map>
#include<stdlib.h>
#include<time.h>
using namespace std;typedef long long ll;ll qmul(ll a,ll b,ll mod){ll res=0;while(b>0){if(b&1)res=(res+a)%mod;a=(a+a)%mod;b>>=1;}return res;
}ll mod_pow(ll x,ll n,ll mod){ll res=1;while(n>0){if(n&1)res=qmul(res,x,mod);x=qmul(x,x,mod);n>>=1;}return res;
}ll random(ll n){return (double)rand()/RAND_MAX*n;
}bool miller_rabin(ll n){if(n==2)return true;if(n<2||n%2==0)return false;ll p=n-1;int k=0;while(p%2==0){p/=2;k++;}for(int i=0;i<10;i++){ll a=random(n-2)+1;ll x=mod_pow(a,p,n),y;for(int j=0;j<k;j++){y=qmul(x,x,n);if(y==1&&x!=1&&x!=n-1)return false;x=y;}if(y!=1)return false;}return true;
}ll Q,P;int main(){int T;scanf("%d",&T);while(T--){scanf("%lld",&P);for(ll i=P-1;;i--){if(miller_rabin(i)){Q=i;break;}}ll res=1;for(ll i=Q+1;i<=P-2;i++){res=qmul(res,i,P);}res=mod_pow(res,P-2,P);printf("%lld\n",res);}return 0;
}

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2019杭电多校第三场 6608 Fansblog（威尔逊定理+miller_rabin素性测试）

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