Re: How to implement x^2-test?

[Action (真的...)]

  我把 Pi 當平均值 (0.5), 不過算起來好像怪怪的...

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/*
        Algorithms Programming Assignment #1
        Random Number Generator

        b5506054
*/

#include <iostream.h>

#define RAND_B 8421
#define RAND_MAX 65536
#define seed_length 55

int seed_table[seed_length];
double x_sqrt = 0;

// (1) pi
bool pi(double x, double y)
{
        return (x * x + y * y <= 1) ? true : false;
}

// (2) integral x^2 dx from 0 to 1
bool sx(double x, double y)
{
        return (y <= x * x) ? true : false;
}

// Linear Congruential method
void rand_init(int seed)
{
        int i;
        *seed_table = seed % RAND_MAX;
        for (i = 1; i < seed_length; i++)
                seed_table[i] = (seed_table[i - 1] * RAND_B + 1) % RAND_MAX;
}

// Additive Congruential method
int rand()
{
        static int ptr = 0;
        ptr = ptr % seed_length;
        seed_table[ptr]
                = (seed_table[ptr] + seed_table[(ptr + 31) % seed_length])
                % RAND_MAX;
        return seed_table[ptr++];
}

// transform from [0, RAND_MAX) to [0, 1)
double random()
{
        double fi = (double) rand() / RAND_MAX;
        x_sqrt += (fi - 0.5) * (fi - 0.5) / 0.5;
        return fi;
}

double calculate(bool (*function) (double x, double y), int times)
{
        int i, n;
        for (i = 0, n = 0; i < times; i++)
                if ((*function) (random(), random()))
                        n++;
        return (double) n / times;
}

void main()
{
        int seed;
        cout << "Please input your seed: ";
        cin >> seed;
        rand_init(seed);
        cout
                << "(1) pi = " << 4.0 * calculate(pi, 10000) << endl
                << "(2) sx = " << calculate(sx, 10000) << endl
                << endl;
        cout
                << "x^2-test:" << endl
                << "  x^2 = " << x_sqrt << endl;
}

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