UVA 10652 - Board Wrapping 簡單計算幾何 凸包

這道題是一個簡單的凸包問題

關鍵的一點就是   把每個塊的四個頂點都求出來   最後排序求凸包      求的時候涉及到角度旋轉   因爲計算機上的三角函數都是弧度制的  轉換的時候注意一點    自己寫的旋轉的函數的角度參數是正的  還是負的 也要注意      否者很容易出錯     

下面看代碼  用的是劉汝佳的模版   本人感覺用着不錯   比自己寫的好多了   計算幾何模版需要高度可靠    

#include<cstdio>
#include<cmath>
#include<algorithm>
#define eps 1e-8
using namespace std;

struct Point
{
    double x,y;
    Point (double x = 0,double y = 0):x(x),y(y){}
};

typedef struct Point Vector;

Vector operator +(Vector A,Vector B)
{
    return Vector(A.x+B.x,A.y+B.y);
}

Vector operator -(Vector A,Vector B)
{
    return Vector(A.x-B.x,A.y-B.y);
}

Vector Rotate(Vector A, double rad)
{
    return Vector(A.x*cos(rad) - A.y*sin(rad),A.x*sin(rad) + A.y*cos(rad));
}

double Cross(Vector A, Vector B)
{
    return A.x*B.y -A.y*B.x;
}

double PolygonArea(Point *p, int n)
{
    double area = 0;
    for(int i = 0 ; i < n-1; i++)
        area += Cross(p[i] - p[0], p[i+1] - p[0]);
    return area / 2;
}

int cmp(Point a,Point b)
{
    if(a.x<b.x)return 1;
    else if(a.x == b.x && a.y < b.y)return 1;
    return 0;
}

int ConvexHull(Point *s,int n,Point *ch)
{
    sort(s,s+n,cmp);
    int m = 0;
    for(int i = 0; i < n; i++)
    {
        while(m >1 && Cross(ch[m-1]-ch[m-2],s[i]-ch[m-2])<= 0)m--;
        ch[m++] = s[i];
    }
    int k = m;
    for(int i = n-2; i >=0; i--)
    {
        while(m > k && Cross(ch[m-1]-ch[m-2],s[i]-ch[m-2]) <= 0)m--;
        ch[m++] = s[i];
    }
    if(n>1)m--;
    return m;
}

int main()
{
    #ifdef LOCAL
    freopen("in.txt","r",stdin);
    #endif // LOCAL
    int T;
    Point p[2500],ch[2500];
    scanf("%d",&T);
    while(T--)
    {
        int n, pc = 0;
        double area1 = 0;
        scanf("%d",&n);
        for(int i = 0; i <n; i++)
        {
            double x,y,w,h,ang,j;
            scanf("%lf%lf%lf%lf%lf",&x,&y,&w,&h,&j);
            Point o(x,y);
            ang = -j*acos(-1)/180.0;//逆時針的角度
            p[pc++] = o + Rotate(Vector(-w/2,-h/2),ang);//因爲Rotate函數的ang是逆時針的
            p[pc++] = o + Rotate(Vector(w/2,-h/2),ang);
            p[pc++] = o + Rotate(Vector(-w/2,h/2),ang);
            p[pc++] = o + Rotate(Vector(w/2,h/2),ang);
            area1 += w*h;
        }
        int m = ConvexHull(p,pc,ch);
        double area2 = PolygonArea(ch,m);
        printf("%.1lf %%\n",area1*100/area2);
    }
    return 0;
}