Вычислить число Пи методом Монте-Карло

#include <iostream>
#include <ctime>
#include <cstdlib>
 
static int rrand(int range_min, int range_max)
{   return rand() % (range_max - range_min + 1) + range_min;
}
 
///----------------------------------------------------------------------------|
/// Ñòàðò.
///----------------------------------------------------------------------------:
int main()
{   srand((unsigned)time(0));
    
    const unsigned NUMBER =  100000;
    unsigned   cnt =              0;
    unsigned  side =           1000;
    unsigned qside =   side *  side;
 
    for(int i = 0; i < NUMBER;  ++i)
    {
        unsigned x = rrand(0, side);
        unsigned y = rrand(0, side);
        
        if((x * x + y * y) < qside) ++cnt;
    }
    
    std::cout << double(cnt*4)/NUMBER << "\n";
}

#include <iostream>
#include <ctime>
#include <cstdlib>
 
// Функция вычисления площади круга радиуса R методом Монте-Карло
double SquareCircle(double R)
{
    const unsigned NUMBER = 10000000;
    double S = 0;
    unsigned cnt = 0;
    for (unsigned i = 0; i < NUMBER; ++i)
    {
        double x = R * rand() / RAND_MAX;
        double y = R * rand() / RAND_MAX;
        if ( x * x + y * y < R*R ) ++cnt;
    }
    return 4.0*R * R*cnt / NUMBER;
}
 
int main()
{
    srand((unsigned)time(0));
 
    double  R = 1.;
    std::cout << SquareCircle(R)/(R*R) << "\n";
    return 0;
}

double SquareCircle(double R)
{
    const unsigned NUMBER = 10000000;
    double S = 0;
    unsigned cnt = 0;
    for (unsigned i = 0; i < NUMBER; ++i)
    {
        double x = (double)rand() / RAND_MAX;
        double y = (double)rand() / RAND_MAX;
        if ( x * x + y * y < 1.0 ) ++cnt;
    }
    return 4.0*R * R*cnt / NUMBER;
}

#include <iostream>
#include <ctime>
#include <cstdlib>
 
inline int rrand(int range_max)
{   return rand() % (range_max + 1);
}
 
///----------------------------------------------------------------------------|
/// Старт. 3,14159
///----------------------------------------------------------------------------:
int main()
{   srand((unsigned)time(0));
    
    const unsigned NUMBER = 100000000  ;
    const unsigned  side  = RAND_MAX   ;
    const unsigned qside  = side * side;
          unsigned cnt    =           0;
 
    for(unsigned i = 0; i < NUMBER;  ++i)
    {   unsigned x = rrand(side),
                 y = rrand(side);
                 
        if ( x*x + y*y  < qside ) ++cnt;
    }
    
    std::cout << (4.*cnt) / NUMBER << "\n";
}