uva 109 SCUD Busters-AC-Upgraded version

//uva 109 SCUD Busters-AC-Upgraded version //AC By Warteac//Runtime:0.009s//2013-5-16/*输入：    第一行的整数，表示输入点的个数    的二行开始，每两个整数表示一个点的坐标    最后一行可以是第一个点（封闭型），也可以是最后一个点（不封闭），但都表示一个封闭的多边形    可以多点共线结果：    凸包的结果存放于grham_scan（）的第二个参数    凸包的顺序是逆时针    构造成功返回true*/ #include<iostream>#include<cstdio>#include<vector>#include<stack>#include <iomanip>#include<algorithm>#include<cmath>using namespace std;typedef int PType;//定义点的类型///////////////////////////////////////struct Point{    PType x,y;    Point(PType a = 0, PType b = 0){x  = a; y = b;}    void print(){cout << "x = " << x << "y = " << y << endl;}     Point operator -(Point p){return Point(x - p.x, y - p.y);} }pBase;//最左下的点typedef Point Vector;//向量int direction(Vector v1,Vector v2){//求两个向量的叉积 return (v1.x*v2.y-v1.y*v2.x); }bool cmp(Point p1, Point p2){//比较函数    int d = direction(p1 - pBase, p2 - pBase);    if(d == 0){//极角相同        return abs(p1.x) < abs(p2.x);//距离从小到大排    }else {        return d < 0;//按逆时针排序    }}bool grham_scan(vector <Point> p , vector <Point> &parray){//求凸包的算法//find first point p0 with minimum y-coordinate or minimun x-coordinate if y are the same    int index = 0;    for(int i = 1; i < p.size(); i++){        if(p[i].y < p[index].y ||(p[i].y == p[index].y && p[i].x < p[index].x))            index = i;    }    swap(p[0],p[index]);    pBase = p[0];    sort(p.begin()+1,p.end(),cmp);//get the convex hull from p    parray.clear();    parray.push_back(p[0]);    parray.push_back(p[1]);    p.push_back(p[0]);    for(int i = 2; i < p.size(); i++){       Vector v1 (p[i].x - parray.back().x, p[i].y - parray.back().y);       Vector v2 (parray.back().x - (parray.end()-2)->x, parray.back().y - (parray.end()-2)->y);       int d = direction(v2,v1);       if(d <= 0) {parray.push_back(p[i]);}       else if(d > 0){        parray.pop_back();i--;        }    }       return true;}int areaOfPolygon(vector <Point> &vecCH) {//求凸多边形的面积    int nArea = 0;    for (vector <Point>::iterator i = vecCH.begin(); i != vecCH.end() - 1; ++i) {        nArea += (i + 1)->x * i->y - i->x * (i + 1)->y;    }    return nArea;}bool inPolygon(Point pt, vector <Point> &vecCH) {//判断点是否在多边形内部    for (vector <Point>::iterator i = vecCH.begin(); i != vecCH.end() - 1; ++i) {        int nX1 = pt.x - i->x, nY1 = pt.y - i->y;        int nX2 = (i + 1)->x - i->x, nY2 = (i + 1)->y - i->y;        if (nX1 * nY2 - nY1 * nX2 < 0) {            return false;        }    }    return true;}//////////////////////////////////////////////////////int main(){    int sites;    PType x,y;    vector <Point> v;    Point t,mi;    vector < vector <Point> >  p;//convex hull    int aflag[105] = {0};    int area = 0;    //input kingdom    while(cin >> sites && sites != -1){        v.clear();        vector <Point> temp;//one convex hull        while(sites--){        cin >> t.x >> t.y;        v.push_back(t);        }        //computing convex hull    if(grham_scan(v,temp) == true){        p.push_back(temp);//all convex hull    }     }     //input missile landings     while(cin >> mi.x >> mi.y){         for(int j = 0; j < p.size(); j++){         if((inPolygon(mi,p[j]) == true) && aflag[j] != 1){         aflag[j] = 1;         area += areaOfPolygon(p[j]);         break;         }     }     }     cout << setiosflags(ios::fixed) << setprecision(2);     cout << (double)area/2.0 << endl; return 0;}