UVA - 143 Orchard Trees （点在三角形内）

  1 #include<cstdio>
  2 #include<cmath>
  3 #include<algorithm>
  4 #include<iostream>
  5 #include<cstring>
  6 using namespace std;
  7 typedef long long ll;
  8 const double eps = 1e-8;
  9 const double pi = acos(-1.0);
 10 const int maxp = 5000;
 11 int sgn(double x)
 12 {
 13     if(fabs(x) < eps) return 0;
 14     else return x < 0 ? -1 : 1;
 15 }
 16 struct Point{
 17     double x, y;
 18     Point(){}
 19     Point(double _x, double _y){
 20         x = _x, y = _y;
 21     }
 22     void input(){
 23         scanf("%lf%lf", &x, &y);
 24     }
 25     bool operator == (Point b) const{
 26         return sgn(x - b.x) == 0 && sgn(y - b.y) == 0;
 27     }
 28     bool operator < (Point b)const{
 29         return sgn(x - b.x) == 0 ? sgn(y - b.y < 0) : x < b.x;
 30     }
 31     Point operator - (const Point &b)const{
 32         return Point(x - b.x, y - b.y);
 33     }
 34     //²æ»ý
 35     double operator ^(const Point &b){
 36         return x * b.y - y * b.x;
 37     }
 38     //µã»ý
 39     double operator *(const Point &b){
 40         return x * b.x + y * b.y;
 41     }
 42     double len(){
 43         return hypot(x, y);
 44     }
 45     double len2(){
 46     return x * x + y * y;
 47     }
 48     double distant(Point p){
 49         return hypot(x - p.x, y - p.y);
 50     }
 51     Point operator + (const Point &b)const{
 52         return Point (x + b.x, y + b.y);
 53     }
 54     Point operator * (const double &k)const{
 55         return Point(x * k, y * k);
 56     }
 57     Point operator / (const double &k)const{
 58         return Point(x / k, y / k);
 59     }
 60 };
 61 struct Line{
 62     Point s, e;
 63     Line(){}
 64     Line(Point _s, Point _e){s = _s, e = _e;}
 65     bool operator == (Line v){
 66         return (s == v.s) && (e == v.e);
 67     }
 68     bool pointonseg(Point p){
 69         return sgn((p - s)^(e - s)) == 0 && sgn((p - e)*(p - s)) <= 0;
 70     }
 71 
 72 };
 73 struct polygon{
 74     int n;
 75     Point p[maxp];
 76     Line l[maxp];
 77     void add(Point q){
 78         p[n ++] = q;
 79     }
 80     void input(int _n){
 81         n = _n;
 82         for(int i = 0;i < n;i++) p[i].input();
 83     }
 84      void getline(){
 85         for(int i = 0;i < n;i++){
 86             l[i] = Line(p[i], p[(i+1) % n]);
 87         }
 88     }
 89     int relationpoint(Point q){
 90         for(int i = 0;i < n;i++){
 91             if(p[i] == q) return 3;
 92         }
 93         getline();
 94         for(int i = 0;i < n;i++){
 95             if(l[i].pointonseg(q)) return 2;
 96         }
 97         int cnt = 0;
 98         for(int i = 0;i < n;i++){
 99             int j = (i + 1) % n;
100             int k = sgn((q - p[j])^(p[i] - p[j]));
101             int u = sgn(p[i].y - q.y);
102             int v = sgn(p[j].y - q.y);
103             if(k > 0 && u < 0 && v >= 0) cnt++;
104             if(k < 0 && v < 0 && u >= 0) cnt--;
105         }
106         return cnt != 0;
107     }
108 };
109 int main()
110 {
111     double x1, x2, x3, y1, y2, y3;
112     polygon a;
113     while(~scanf("%lf%lf%lf%lf%lf%lf",&x1, &y1, &x2, &y2, &x3, &y3) && (x1|| x2|| x3|| y1|| y2|| y3))
114     {
115         a.n = 0;
116         a.add(Point(x1,y1));
117         a.add(Point(x2,y2));
118         a.add(Point(x3,y3));
119         int cnt = 0;
120         for(double i = 1;i <= 99;i++)
121             for(double j = 1;j <= 99;j++)
122                 if(a.relationpoint(Point(i,j))) cnt ++;
123         printf("%4d\n",cnt);
124     }
125     return 0;
126 }