#include<iostream>

#include<stdlib.h>

#include<time.h>

using namespace std;

double rand_num()

{//产生随机数函数

double ran_double = rand() / (double)(RAND_MAX);

return ran_double;

}

double rand_a_b(double a, double b)

{//产生a，b之间的随机数

double rand_double = a + (b - a)*rand() / (RAND_MAX);

return rand_double;

}

double fun(double x, double y)

{//函数x*x+y*y的值

double temp;

temp = x*x + y*y;

return temp;

}

double fun1(double x)

{//求函数sqrt(1 - x*x)的值

double temp;

temp = sqrt(1 - x*x);

return temp;

}

double fun_sin(double x)

{

return sin(x);

}

double HitorMiss(double a, double b, double c, double d, double (*fun)(double))

{//四个参数，a,b;c,d;和函数指针fun

double x, y;

double M = 1e1;

int m = 0;

for (int i = 0; i < M; i++)

{

x = rand_a_b(a, b);

y = rand_a_b(c, d);

if (y <= fun(x))

m++;

}

return (m / (M + 0.0)*(b - a)*(d - c));

}

void main()

{

srand((unsigned)time(NULL));

//double M = 1e1; //循环次数

//cout << M<<endl;

//double x, y;

//for (int j = 0; j < 8; j++)

//{

// int m = 0;

// for (int i = 0; i < M; i++)

// {

// x = rand_num();

// y = rand_num();

// //y = x;

// if (y <= fun1(x))

// m++;

// }

// cout << "当n=" << M << "时，结果为：" << 4 * m / (M + 0.0) << endl;

// M *= 10;

//}

//cout << rand_a_b(2.5, 4.3);

for (int i = 0; i < 5; i++)

{

cout << "通过概率计算sin（x）在[0，1]上积分值：" << HitorMiss(0, 1.0, 0, 0.85, fun_sin) << endl;

}

system("pause");

}

//多次循环的值 //计算x=y时结果

//for (int j = 0; j < 10; j++)

//{

// int m = 0;

// for (int i = 0; i < M; i++)

// {

// x = rand() / double(RAND_MAX);//产生0-1之间随机数

// y = x; //将x赋值给y

// if (x*x + y*y <= 1)

// m++;

// }

// cout << "当n=" << M << "时，结果为：" << 4 * m / (M + 0.0) << endl;

// M *= 10;

//}

/*cout << m << endl;

double Pi = 4 * m /( M + 0.0);

cout << "PI:" << Pi << endl;*/