poj 3277 Mountains

http://poj.org/problem?id=3227

 #include <cstdio>
 #include <cstring>
 #include <cmath>
 #include <algorithm>
 #define maxn 2000
 using namespace std;

 int n,h;
 const double eps=1e-;
 int cmp(double x)
 {
     if(fabs(x)<eps) return ;
     if(x>) return ;
     return -;
 }
 struct point
 {
     double x,y;
     point() {}
     point(double a,double b):x(a),y(b) {}
 } p[maxn];

 double sqr(double x)
 {
     return x*x;
 }

 double dis(point a,point b)
 {
     return (sqrt(sqr(a.x-b.x)+sqr(a.y-b.y)));
 }

 double det(point a,point b,point c,point d)
 {
     return (b.x-a.x)*(d.y-c.y)-(b.y-a.y)*(d.x-c.x);
 }

 bool segem(point a,point b,point c,point d,point &e)
 {
     double s1=det(a,b,a,c);
     double s2=det(a,b,a,d);
     e.x=(c.x*s2-d.x*s1)/(s2-s1);
     e.y=(c.y*s2-d.y*s1)/(s2-s1);
     return true;
 }

 double kk(point a,point b)
 {
     return (b.y-a.y)/(b.x-a.x);
 }
 int main()
 {
     while(scanf("%d%d",&n,&h)!=EOF)
     {
         if(n==&&h==) break;
         for(int i=; i<n; i++)
         {
             scanf("%lf%lf",&p[i].x,&p[i].y);
         }
         point res;
         res.x=;
         res.y=h;
         double sum=;
         sum+=dis(p[],p[]);
         point key;
         key=p[];
         for(int i=; i<n; i++)
         {
             double k3=kk(res,p[i]);
             double k1=kk(p[i],p[i-]);
             double k2=kk(res,key);
             if(k3-k2>eps)
             {
                 if(k1-k2>=)
                 {
                     point e;
                     segem(res,key,p[i-],p[i],e);
                     sum+=dis(e,p[i]);
                     key=p[i];
                 }
             }
         }
         printf("%.2lf\n",sum);
     }
     return ;
 }