Solution to Monte Carlo problem for Coding Dojo Feb 2012 by Mims H. Wright (in C++)

montecarlo.cpp

#include <iostream>
#include <stdlib.h>
#include <cmath>
#include <ctime>
using namespace std;
int main()
{
	int reps = 0;
	cout << "Enter number of repititions then press enter." << endl;
	cin >> reps;
	cout << "Calculating π in " << reps << " steps" << endl;
	
	// initialize random seed:
	srand ( time(0) );
	
	int i = 0, inCircle = 0;
	double x = 0, y = 0, d = 0.0;
	while (i++ < reps) {
		x = ((double) rand() / RAND_MAX);
		y = ((double) rand() / RAND_MAX);
		
		// Find the distance from the origin. If it's less than the radius of the circle, it's inside the circle. 
		d = sqrt( x*x + y*y );
		inCircle += d < 1 ? 1 : 0;
	}
	
	double pi = ((double)inCircle / reps) * 4.0;
	cout << "Pi is roughly " << pi << endl;
	
	return 0;
}