poj1113Wall(凸包）

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顺便整理出来一份自己看着比较顺眼的模板

 #include <iostream>
 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 #include<stdlib.h>
 #include<vector>
 #include<cmath>
 #include<queue>
 #include<set>
 using namespace std;
 #define N 1010
 #define LL long long
 #define INF 0xfffffff
 const double eps = 1e-;
 const double pi = 3.141592653;
 const double inf = ~0u>>;
 struct Point
 {
     double x,y;
     Point(double x=,double y=):x(x),y(y) {} //构造函数 方便代码编写
 }p[N],ch[N];
 typedef Point pointt;
 pointt operator + (Point a,Point b)
 {
     return Point(a.x+b.x,a.y+b.y);
 }
 pointt operator - (Point a,Point b)
 {
     return Point(a.x-b.x,a.y-b.y);
 }
 pointt operator * (Point a,double b)
 {
     return Point(a.x*b,a.y*b);
 }
 pointt operator / (Point a,double b)
 {
     return Point(a.x/b,a.y/b);
 }
 bool operator < (const Point &a,const Point &b)
 {
     return a.x<b.x||(a.x==b.x&&a.y<b.y);
 }
 int dcmp(double x)
 {
     if(fabs(x)<eps) return ;
     else return x<?-:;
 }
 bool operator == (const Point &a,const Point &b)
 {
     return dcmp(a.x-b.x)==&&dcmp(a.y-b.y)==;
 }
 //求点积以及利用点积求长度和夹角的函数
 double dot(Point a,Point b)
 {
     return a.x*b.x+a.y*b.y;
 }
 //叉积及叉积求面积
 double cross(Point a,Point b)
 {
     return a.x*b.y-a.y*b.x;
 }
 double  dis(Point a)
 {
     return sqrt(dot(a,a));
 }
 double mul(Point p0,Point p1,Point p2)
 {
     return cross(p1-p0,p2-p0);
 }
 bool cmp(Point a,Point b)
 {
     if(dcmp(mul(p[],a,b))==)
         return dis(a-p[])<dis(b-p[]);
     else
         return dcmp(mul(p[],a,b))>;
 }
 int Graham(int n)
 {
     int i,k = ,top = ;
     Point tmp;
     if(n<=)
     {
         for(i = ; i <=  ; i++)
             ch[i] = p[i];
         return n+;
     }
     for(i =  ; i <= n; i++)
     {
         if(p[i].y<p[k].y||(p[i].y==p[k].y&&p[i].x<p[k].x))
             k = i;
     }
     if(k!=)
     {
         tmp = p[];  p[] = p[k];  p[k] = tmp;
     }
     sort(p+,p+n+,cmp);
     ch[top++] = p[];
     ch[top++] = p[];
     ch[top++] = p[];
     for(i = ; i <= n ;)
     {
         if(top<||mul(ch[top-],ch[top-],p[i])>)
         {
             ch[top++] = p[i++];
         }
         else  top--;
     }
     return top;
 }
 int main()
 {
     int i,n,r;
     while(scanf("%d%d",&n,&r)!=EOF)
     {
         for(i =  ; i <= n ; i++)
         {
             scanf("%lf%lf",&p[i].x,&p[i].y);
         }
         int top = Graham(n);
         ch[top] = p[];
         double ma;
         ma = *pi*r;
         for(i =  ; i < top ; i++)
         {
             ma += dis(ch[i]-ch[i+]);
         }
         printf("%.0f\n",ma);
     }
     return ;
 }