UVa10652

题目链接：https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=1593

把每个矩形的四个顶点都找出来，做凸包就是最小的多边形，计算面积就从一个点出发向每个点都连一条对角线，将多边形分成若干个三角形再计算。

比较坑的是，数字和“%”之间还有一个空格>_<!

#include <iostream>#include <cstdio>#include <cmath>#include <algorithm>using namespace std;struct Point{    double x, y;    Point() {};    Point(double x, double y):x(x), y(y) {}    bool operator < (const Point& a) const    {        if (x == a.x)            return y < a.y;        return x < a.x;    }    bool operator == (const Point& a) const    {        if (x == a.x && y == a.y)            return true;        return false;    }};typedef Point Vector;Point P[2500], convex[2500];Vector operator - (const Point& A, const Point& B){    return Vector(A.x-B.x, A.y-B.y);}Point operator + (const Point& A, const Vector& a){    return Point(A.x+a.x, A.y+a.y);}double Cross(Vector A, Vector B){    return A.x*B.y - A.y*B.x;}double Area( Point A, Point B, Point C){    return Cross(A-B, A-C) / 2;}Vector Rotate(const Vector& A, double rad) //顺时针旋转向量A{    return Vector(A.x*cos(rad)-A.y*sin(rad), A.x*sin(rad)+A.y*cos(rad));}int ConvexHull(Point* p, int n, Point* ch){    sort(p, p+n);    n = unique(p, p+n) - p;    int m = 0;    for (int i=0; i<n; i++)    {        while (m > 1 && Cross(ch[m-1]-ch[m-2], p[i]-ch[m-2]) <= 0) m--;        ch[m++] = p[i];    }    int k = m;    for (int i=n-2; i>=0; i--)    {        while (m > k && Cross(ch[m-1]-ch[m-2], p[i]-ch[m-2]) <= 0) m--;        ch[m++] = p[i];    }    return m;}int main(){    int T;    scanf("%d",&T);    while (T > 0)    {        T--;        int n;        double RecArea = 0;        scanf("%d",&n);        int cnt = 0;        for (int i=0; i<n; i++)        {            double x, y, w, h, j;            scanf("%lf%lf%lf%lf%lf",&x,&y,&w,&h,&j);            RecArea += w*h;            Point centre(x,y);            Vector v1(w/2,h/2), v2(w/2,-h/2), v3(-w/2, h/2), v4(-w/2,-h/2);            Point p1 = centre + Rotate(v1,-j/180*3.1415926);            Point p2 = centre + Rotate(v2,-j/180*3.1415926);            Point p3 = centre + Rotate(v3,-j/180*3.1415926);            Point p4 = centre + Rotate(v4,-j/180*3.1415926);            P[cnt++] = p1; P[cnt++] = p2; P[cnt++] = p3; P[cnt++] = p4;        }        n = ConvexHull(P,cnt,convex);        double ConvexArea = 0;        for (int i=1; i<n-1; i++)            ConvexArea += Area(convex[0],convex[i],convex[i+1]);        double ans = RecArea / ConvexArea * 100;        printf("%.1lf ",ans);        cout << '%' << endl;    }    return 0;}