hdu 5295 Unstable（计算几何）

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题目链接：hdu 5295 Unstable

先确定B，C点，再找到A‘点A’C = AD，A'B = 2EF，然后确定G点向量A'G = CB（注意是向量）。然后根据DG = AB确定D点。三角形DAF和FBA‘为全等三角形，所以A点也可以得到。

#include <cstdio>#include <cstring>#include <cmath>#include <algorithm>using namespace std;const double eps = 1e-9;inline int sgn(double x) {return x < 0 ? -1 : 1;}struct Point {double x, y;Point (double x = 0, double y = 0) {set(x, y);}void set(double x, double y) {this->x = x;this->y = y;}void put() {printf("%lf %lf\n", x, y);}Point operator - (const Point& a) {Point ret;ret.set(x - a.x, y - a.y);return ret;}Point operator + (const Point& a) {Point ret;ret.set(x + a.x, y + a.y);return ret;}bool operator == (const Point& a) {return fabs(x - a.x) < eps && fabs(y - a.y) < eps;}};struct Circle {Point o;double r;void set(Point o, double r) {this->o = o;this->r = r;}bool operator == (const Circle& a) {return o == a.o && fabs(r - a.r) < eps;}};Circle P, Q;Point A, A2, B, C, D, G, T;double AB, BC, CD, DA, EF;void getPoint(Circle p, Circle q, Point& u, Point& v) {if (p == q) {u = p.o + Point(0, p.r);v = p.o - Point(0, p.r);return;}double a = q.o.x - p.o.x, b = q.o.y - p.o.y;double c = (pow(p.r, 2) - pow(q.r, 2) + a * a + b * b) / 2;if (fabs(a) > eps && fabs(b) > eps) {double delta = b * b * c * c - (a * a + b * b) * (c * c - p.r * p.r * a * a);if (sgn(delta) <= 0)delta = 0;u.y = (b * c + sqrt(delta)) / (a * a + b * b);v.y = (b * c - sqrt(delta)) / (a * a + b * b);u.x = (c - b * u.y) / a;v.x = (c - b * u.y) / a;} else if (fabs(a) > eps && fabs(b) < eps) {u.x = v.x = c / a;double tmp = p.r * p.r - u.x * u.x;if (sgn(tmp) <= 0)tmp = 0;u.y = sqrt(tmp);v.y = -u.y;} else if (fabs(a) < eps && fabs(b) > eps) {u.y = v.y = c / b;double tmp = p.r * p.r - u.y * u.y;if (sgn(tmp) <= 0)tmp = 0;u.x = sqrt(tmp);v.x = -u.x;}u = u + p.o;v = v + p.o;}void solve () {B.set(0, 0);C.set(BC, 0);P.set(B, 2 * EF);Q.set(C, DA);getPoint(P, Q, A2, T);G = A2 + (B - C);P.set(G, AB);Q.set(C, CD);getPoint(P, Q, D, T);A = D + (C - A2);}int main () {int cas;scanf("%d", &cas);for (int kcas = 1; kcas <= cas; kcas++) {scanf("%lf%lf%lf%lf%lf", &AB, &BC, &CD, &DA, &EF);printf("Case #%d:\n", kcas);solve();A.put();B.put();C.put();D.put();}return 0;}

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