shapes

circle.cpp

// Draws a circle

#include <iostream>

using namespace std;

int
main(void)
{
	int r;	//radius
	
	// The circle is centered at the origin.
	
	r = 20;
	for(int y = r; y >= -r; y--){
		for(int x = -r; x <= r; x++){
			if(x*x + y*y <= r*r)
				cout << '*';
			else
				cout << ' ';
		}
		cout << endl;
	}
	return 0;
}

equilateral.cpp

// Draws an equilateral triangle

#include <iostream>
#include <cmath>

using namespace std;

int
main(void)
{
	int n;	// half of length of each sides
	
	// The three corners of the triangle are at:
	//	(-n, 0), (n, 0), and (0, n*sqrt(3))
	//
	// The line going from (-n, 0) to (0, n*sqrt(3)) is:
	//	y = sqrt(3)*x + sqrt(3)*n
	//
	// The line going from (n, 0) to (0, n*sqrt(3)) is:
	//	y = -sqrt(3)*x + sqrt(3)*n
	
	n = 40/2;
	for(int y = n*sqrt(3); y >= 0; y--){
		for(int x = -n; x <= n; x++){
			if(y <= sqrt(3)*x + sqrt(3)*n 
			&& y <= -sqrt(3)*x + sqrt(3)*n)
				cout << '*';
			else
				cout << ' ';
		}
		cout << endl;
	}
}