素數性測試的蒙特卡羅演算法

#include<iostream>

#include<time.h>

 

using namespace std;

 

long Pow(int a,int b) //計算a的b次方

{

       intk;

       longs=1;

       for(k=1;k<=b;k++)

       {

              s*=a;

       }

       returns;

}

bool RandomPrimalityTest(int N) //蒙特卡羅測試

{

       srand((unsigned)time(NULL));//初始化隨機種子

       inta=rand()%N; //隨機產生小於N的整數

       if(a==0)a=N-1;

       longb=Pow(a,N-1)-1;

       if(b%N==0)return true;

       elsereturn false;

}

 

void RepeatCall(int N,int n=100) //重複調用RandomPrimalityTest函數n次

{

       intk;

       intcnt=0;

       constdouble precison=0.90; //定義精度

       for(k=1;k<=n;k++)if(RandomPrimalityTest(N)) cnt++;

       doublee=cnt*1.0/n;

       if(e>=precison)cout<<N<<"是素數"<<endl;

       elsecout<<N<<"不是素數"<<endl;

}

 

void main()

{

       intN;

       cout<<"請輸入一個整數:";

       cin>>N;

       if(!cin.good())

       {

              cerr<<"輸入異常!"<<endl;

              cin.clear();

              return;

       }

       RepeatCall(N);

}