글 읽기 - 반도의 흔한 실수형 타입 변수 -0.0000

lsc4719 8년 전 0

-0.000000

0.000000

-0.000000이 출력되는 이유가 무엇일까요?

#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <utility>
using namespace std;

class vector2 {
public:
	double x, y;
	vector2(){}
	vector2(double x, double y) : x(x), y(y){}
	vector2 operator + (const vector2& rhs) const {
		return vector2(x + rhs.x, y + rhs.y);
	}
	vector2 operator - (const vector2& rhs) const {
		return vector2(x - rhs.x, y - rhs.y);
	}
	double operator * (const vector2& rhs) const {
		return (x * rhs.x + y * rhs.y);
	}
	double operator ^ (const vector2& rhs) const {
		return (x * rhs.y - y * rhs.x);
	}
};

class lineEquation {
public:
	double a, b, c;
	lineEquation(){}
	lineEquation(double a, double b, double c) : a(a), b(b), c(c){}
};

lineEquation findLineEquationFromTwoPoints(vector2 u, vector2 v) {
	double a = u.y - v.y;
	double b = v.x - u.x;
	double c = a * u.x + b * u.y;
	return lineEquation(a, b, c);
}

lineEquation findOrthogonalLineOfLinePassingPoint(lineEquation u, vector2 v) {
	double a = -u.b;
	double b = u.a;
	double c = a * v.x + b * v.y;
	return lineEquation(a, b, c);
}

pair<bool, vector2> findIntersectionPointOfTwoLines(lineEquation u, lineEquation v) {
	double determinant = u.a * v.b - u.b * v.a;
	double x, y;
	if (determinant == 0) return make_pair(false, vector2());
	x = (v.b * u.c - u.b * v.c) / determinant;
	y = (-v.a * u.c + u.a * v.c) / determinant;
	return make_pair(true, vector2(x, y));
}

vector2 findCenterOfCircleFromThreePoints(vector2 *pt) {
	lineEquation u, v;
	u = findLineEquationFromTwoPoints(pt[0], pt[1]);
	v = findLineEquationFromTwoPoints(pt[1], pt[2]);
	vector2 middlePoint1 = vector2((pt[0].x + pt[1].x) / 2.0, (pt[0].y + pt[1].y) / 2.0);
	vector2 middlePoint2 = vector2((pt[1].x + pt[2].x) / 2.0, (pt[1].y + pt[2].y) / 2.0);
	u = findOrthogonalLineOfLinePassingPoint(u, middlePoint1);
	v = findOrthogonalLineOfLinePassingPoint(v, middlePoint2);
	pair<bool, vector2> res = findIntersectionPointOfTwoLines(u, v);
	return res.second;
}

int main() {
	vector2 *pt = (vector2 *)malloc(3 * sizeof(vector2));
	
	printf("서로 동일한 원 위에 있는 이차원상의 세 점의 좌표를 입력하세요 : ");
	for (int i = 0; i < 3; i++) {
		scanf("%lf %lf", &pt[i].x, &pt[i].y);
	}

	vector2 centerOfCircle = findCenterOfCircleFromThreePoints(pt);
	double radiusOfCircle = sqrt((pt[0] - centerOfCircle) * (pt[0] - centerOfCircle));
	printf("원의 중심점은 (%.8lf, %.8lf)이고 원의 반지름은 %lf입니다.\n", centerOfCircle.x, centerOfCircle.y, radiusOfCircle);

	free(pt);

	return 0;
}