计算几何板..

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <iostream>
 4 #include <cmath>
 5 #include <algorithm>
 6 using namespace std;
 7 
 8 const double eps = 1e-8;
 9 const int maxn = 1000+5;
10 int n;
11 
12 int dcmp(double x){
13     if(fabs(x) < eps) return 0;
14     if(x < 0) return -1;
15     return 1;
16 }
17 
18 struct Point{
19     double x,y;
20     Point(){}
21     Point(double _x,double _y){
22         x = _x;y = _y;
23     }
24     Point operator - (const Point &b) const{
25         return Point(x-b.x,y-b.y);
26     }
27     Point operator + (const Point &b) const{
28         return Point(x+b.x,y+b.y);
29     }
30     double operator ^ (const Point &b) const{//叉积
31         return x*b.y - y*b.x;
32     }
33     double operator * (const Point &b) const{//点积
34         return x*b.x + y*b.y;
35     }
36 };
37 
38 struct Line{
39     Point s,e;
40     Line(){}
41     Line(Point _s,Point _e){
42         s = _s;e = _e;
43     }
44 };
45 
46 double xmult(Point p0,Point p1,Point p2){
47     return (p1-p0) ^ (p2-p0);
48 }
49 
50 bool Seg_inter_line(Line l1,Line l2){
51     return dcmp(xmult(l2.s,l1.s,l1.e)) * dcmp(xmult(l2.e,l1.s,l1.e)) <= 0;
52 }
53 
54 double dis(Point a,Point b){
55     return sqrt( (b-a) * (b-a) );
56 }
57 
58 Line line[maxn];
59 
60 bool check(Line l1){
61     if(dcmp(dis(l1.s,l1.e)) == 0) return false;
62     for(int i = 0;i < n;i++) {
63         if(Seg_inter_line(l1,line[i]) == false) return false;
64     }
65     return true;
66 }
67 
68 void solve(){
69     for(int i = 0;i < n;i++){
70         for(int j = 0;j < n;j++){
71             Point a = line[i].s;
72             Point b = line[i].e;
73             Point c = line[j].s;
74             Point d = line[j].e;
75             if(check(Line(a,c)) || check(Line(a,d)) || check(Line(b,c)) || check(Line (b,d))){
76                 puts("Yes!");
77                 return;
78             }
79         }
80     }
81     puts("No!");
82 }
83 
84 int main(){
85     int T;
86     scanf("%d",&T);
87     while(T--){
88         scanf("%d",&n);
89         double x1,x2,y1,y2;
90         for(int i = 0;i < n;i++){
91             scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2);
92             line[i] = Line(Point(x1,y1),Point(x2,y2));
93         }
94         solve();
95     }
96     return 0;
97 }