UVA 11796 Dog Distance（向量）

题目链接：http://acm.hust.edu.cn/vjudge/problem/viewProblem.action?id=31962
【代码】
 1 #include<cstdio>
 2 #include<cmath>
 3 #include<algorithm>
 4 using namespace std;
 5 
 6 const double eps = 1e-8;
 7 int dcmp(double x) { if(fabs(x) < eps) return 0; else return x < 0 ? -1 : 1; }
 8 
 9 struct Point {
10   double x, y;
11   Point(double x=0, double y=0):x(x),y(y) { }
12 };
13 
14 typedef Point Vector;
15 
16 Vector operator + (const Vector& A, const Vector& B) { return Vector(A.x+B.x, A.y+B.y); }
17 Vector operator - (const Point& A, const Point& B) { return Vector(A.x-B.x, A.y-B.y); }
18 Vector operator * (const Vector& A, double p) { return Vector(A.x*p, A.y*p); }
19 Vector operator / (const Vector& A, double p) { return Vector(A.x/p, A.y/p); }
20 
21 bool operator < (const Point& a, const Point& b) {
22   return a.x < b.x || (a.x == b.x && a.y < b.y);
23 }
24 
25 bool operator == (const Point& a, const Point &b) {
26   return dcmp(a.x-b.x) == 0 && dcmp(a.y-b.y) == 0;
27 }
28 
29 Point read_point() {
30   double x, y;
31   scanf("%lf%lf", &x, &y);
32   return Point(x, y);
33 };
34 
35 double Dot(const Vector& A, const Vector& B) { return A.x*B.x + A.y*B.y; }
36 double Length(const Vector& A) { return sqrt(Dot(A, A)); }
37 double Cross(const Vector& A, const Vector& B) { return A.x*B.y - A.y*B.x; }
38 
39 double DistanceToSegment(const Point& P, const Point& A, const Point& B) {
40   if(A == B) return Length(P-A);
41   Vector v1 = B - A, v2 = P - A, v3 = P - B;
42   if(dcmp(Dot(v1, v2)) < 0) return Length(v2);
43   else if(dcmp(Dot(v1, v3)) > 0) return Length(v3);
44   else return fabs(Cross(v1, v2)) / Length(v1);
45 }
46 
47 const int maxn = 60;
48 int T, A, B;
49 Point P[maxn], Q[maxn];
50 double Min, Max;
51 
52 void update(Point P, Point A, Point B) {
53   Min = min(Min, DistanceToSegment(P, A, B));
54   Max = max(Max, Length(P-A));
55   Max = max(Max, Length(P-B));
56 }
57 
58 int main() {
59   scanf("%d", &T);
60   for(int kase = 1; kase <= T; kase++) {
61     scanf("%d%d", &A, &B);
62     for(int i = 0; i < A; i++) P[i] = read_point();
63     for(int i = 0; i < B; i++) Q[i] = read_point();
64 
65     double LenA = 0, LenB = 0;
66     for(int i = 0; i < A-1; i++) LenA += Length(P[i+1]-P[i]);
67     for(int i = 0; i < B-1; i++) LenB += Length(Q[i+1]-Q[i]);
68 
69     int Sa = 0, Sb = 0;
70     Point Pa = P[0], Pb = Q[0];
71     Min = 1e9, Max = -1e9;
72     while(Sa < A-1 && Sb < B-1) {
73       double La = Length(P[Sa+1] - Pa);
74       double Lb = Length(Q[Sb+1] - Pb);
75       double T = min(La/LenA, Lb/LenB); 
76       Vector Va = (P[Sa+1] - Pa)/La*T*LenA;
77       Vector Vb = (Q[Sb+1] - Pb)/Lb*T*LenB; 
78       update(Pa, Pb, Pb+Vb-Va);
79       Pa = Pa + Va;
80       Pb = Pb + Vb;
81       if(Pa == P[Sa+1]) Sa++;
82       if(Pb == Q[Sb+1]) Sb++;
83     }
84     printf("Case %d: %.0lf
", kase, Max-Min);
85   }
86   return 0;
87 }