UVA 11796 Dog Distance（向量）

题目链接：http://acm.hust.edu.cn/vjudge/problem/viewProblem.action?id=31962

【代码】

 #include<cstdio>
 #include<cmath>
 #include<algorithm>
 using namespace std;

 const double eps = 1e-;
 int dcmp(double x) { if(fabs(x) < eps) return ; else return x <  ? - : ; }

 struct Point {
   double x, y;
   Point(double x=, double y=):x(x),y(y) { }
 };

 typedef Point Vector;

 Vector operator + (const Vector& A, const Vector& B) { return Vector(A.x+B.x, A.y+B.y); }
 Vector operator - (const Point& A, const Point& B) { return Vector(A.x-B.x, A.y-B.y); }
 Vector operator * (const Vector& A, double p) { return Vector(A.x*p, A.y*p); }
 Vector operator / (const Vector& A, double p) { return Vector(A.x/p, A.y/p); }

 bool operator < (const Point& a, const Point& b) {
   return a.x < b.x || (a.x == b.x && a.y < b.y);
 }

 bool operator == (const Point& a, const Point &b) {
   return dcmp(a.x-b.x) ==  && dcmp(a.y-b.y) == ;
 }

 Point read_point() {
   double x, y;
   scanf("%lf%lf", &x, &y);
   return Point(x, y);
 };

 double Dot(const Vector& A, const Vector& B) { return A.x*B.x + A.y*B.y; }
 double Length(const Vector& A) { return sqrt(Dot(A, A)); }
 double Cross(const Vector& A, const Vector& B) { return A.x*B.y - A.y*B.x; }

 double DistanceToSegment(const Point& P, const Point& A, const Point& B) {
   if(A == B) return Length(P-A);
   Vector v1 = B - A, v2 = P - A, v3 = P - B;
   if(dcmp(Dot(v1, v2)) < ) return Length(v2);
   else if(dcmp(Dot(v1, v3)) > ) return Length(v3);
   else return fabs(Cross(v1, v2)) / Length(v1);
 }

 const int maxn = ;
 int T, A, B;
 Point P[maxn], Q[maxn];
 double Min, Max;

 void update(Point P, Point A, Point B) {
   Min = min(Min, DistanceToSegment(P, A, B));
   Max = max(Max, Length(P-A));
   Max = max(Max, Length(P-B));
 }

 int main() {
   scanf("%d", &T);
   for(int kase = ; kase <= T; kase++) {
     scanf("%d%d", &A, &B);
     for(int i = ; i < A; i++) P[i] = read_point();
     for(int i = ; i < B; i++) Q[i] = read_point();

     double LenA = , LenB = ;
     for(int i = ; i < A-; i++) LenA += Length(P[i+]-P[i]);
     for(int i = ; i < B-; i++) LenB += Length(Q[i+]-Q[i]);

     int Sa = , Sb = ;
     Point Pa = P[], Pb = Q[];
     Min = 1e9, Max = -1e9;
     while(Sa < A- && Sb < B-) {
       double La = Length(P[Sa+] - Pa);
       double Lb = Length(Q[Sb+] - Pb);
       double T = min(La/LenA, Lb/LenB);
       Vector Va = (P[Sa+] - Pa)/La*T*LenA;
       Vector Vb = (Q[Sb+] - Pb)/Lb*T*LenB;
       update(Pa, Pb, Pb+Vb-Va);
       Pa = Pa + Va;
       Pb = Pb + Vb;
       if(Pa == P[Sa+]) Sa++;
       if(Pb == Q[Sb+]) Sb++;
     }
     printf("Case %d: %.0lf\n", kase, Max-Min);
   }
   return ;
 }