pku 1410(判断线段是否跟矩形相交)

 1 /*
 2 *  题目要求：判断线段是否跟矩形相交 
 3 *  注意：线段完全在矩形内也是相交 
 4 *  解法：分别判断线段是否跟矩形的四条边相交，再判断线段的两个端点是否都在矩形内 
 5 */
 6 
 7 #include <cstdio>
 8 #include <cstdlib>
 9 #include <iostream>
10 
11 using namespace std;
12 
13 struct point {
14     double x;
15     double y;
16 }A, B, C, D, E, F;
17 
18 double crossProd(point A, point B, point C) {
19     return (B.x-A.x)*(C.y-A.y) - (B.y-A.y)*(C.x-A.x);
20 }
21 
22 bool segIntersect(point A, point B, point C, point D) {//判断线段是否相交 
23     if (max(A.x, B.x) >= min(C.x, D.x) &&
24         max(C.x, D.x) >= min(A.x, B.x) &&
25         max(A.y, B.y) >= min(C.y, D.y) &&
26         max(C.y, D.y) >= min(A.y, B.y) &&
27         crossProd(C, D, A)*crossProd(C, B, D)>=0 &&
28         crossProd(A, B, C)*crossProd(A, D, B)>=0) return true;
29     return false;
30 }
31 
32 bool pointInRectangle(point S, point A, point B) {//判断点是否在矩形内 
33     if (max(A.x, B.x) >= S.x &&
34         min(A.x, B.x) <= S.x &&
35         max(A.y, B.y) >= S.y &&
36         min(A.y, B.y) <= S.y) return true;
37     return false;
38 }
39 
40 bool segXRectangle() {
41     if (segIntersect(A, B, C, E)) return true;//判断线段是否跟矩形的边相交 
42     else if (segIntersect(A, B, C, F)) return true;
43     else if (segIntersect(A, B, D, E)) return true;
44     else if (segIntersect(A, B, D, F)) return true;
45     if (pointInRectangle(A, C, D) && pointInRectangle(B, C, D)) return true;//判断线段的两端点是否都在矩形内 
46     return false;
47 }
48 
49 int main() {
50     int t;
51     scanf ("%d", &t);
52     while (t--) {
53         scanf ("%lf%lf%lf%lf%lf%lf%lf%lf", &A.x, &A.y, &B.x, &B.y, &C.x, &C.y, &D.x, &D.y);
54         E.x = C.x;
55         E.y = D.y;
56         F.x = D.x;
57         F.y = C.y;
58         bool yes = segXRectangle();
59         if (yes) printf ("T\n");
60         else printf ("F\n");
61     }
62     return 0;
63 }
posted on 2012-04-25 13:11 Try86 阅读(426) 评论(0) 收藏举报