poj 1113 Wall (凸包模板题）

  1 /*************************************************************************
  2     > File Name: code/poj/1113.cpp
  3     > Author: 111qqz
  4     > Email: rkz2013@126.com 
  5     > Created Time: 2015年11月09日 星期一 16时33分28秒
  6  ************************************************************************/
  7 
  8 #include<iostream>
  9 #include<iomanip>
 10 #include<cstdio>
 11 #include<algorithm>
 12 #include<cmath>
 13 #include<cstring>
 14 #include<string>
 15 #include<map>
 16 #include<set>
 17 #include<queue>
 18 #include<vector>
 19 #include<stack>
 20 #include<cctype>
 21 #define fst first              
 22 #define sec second      
 23 #define lson l,m,rt<<1
 24 #define rson m+1,r,rt<<1|1
 25 #define ms(a,x) memset(a,x,sizeof(a))
 26 using namespace std;
 27 const double eps = 1E-8;
 28 const int dx4[4]={1,0,0,-1};
 29 const int dy4[4]={0,-1,1,0};
 30 typedef long long LL;
 31 const int inf = 0x3f3f3f3f;
 32 const double pi = acos(-1.0);
 33 const int N=1E3+7;
 34 int n,l;
 35 int top;
 36 int dblcmp(int d)
 37 {
 38     return d<-eps?-1:d>eps;
 39 }
 40 struct point 
 41 {
 42     double x,y;
 43     point (){}
 44     point (double _x,double _y):
 45     x(_x),y(_y){};
 46 
 47     void input()
 48     {
 49     scanf("%lf %lf",&x,&y);
 50     }
 51     point operator - (const point &p) const{
 52     return point (x-p.x,y-p.y);
 53     }
 54     double operator ^ (const point  &p) const{
 55     return x*p.y-y*p.x;
 56     }
 57     bool operator < (const point a)const{
 58     return dblcmp(a.x-x)==0?dblcmp(y-a.y)<0:x<a.x;
 59     }
 60     double distance(point p)
 61     {
 62     return hypot(x-p.x,y-p.y);
 63     }
 64     point sub(point p)
 65     {
 66     return point(x-p.x,y-p.y);
 67     }
 68 
 69     double det(point p)
 70     {
 71     return x*p.y-y*p.x;
 72     }
 73 
 74     
 75 }p[N];
 76 
 77 
 78 struct polygon
 79 {
 80     point p[N];
 81     int n;
 82     void input()
 83     {
 84     
 85     p[0].input();
 86     for ( int i = 1 ; i < n ; i++)
 87     {
 88         p[i].input();
 89         if (p[i].y>p[0].y||(p[i].y==p[0].y&&p[i].x>p[0].x))
 90         swap(p[0],p[i]);
 91     }
 92     }
 93 
 94     struct cmp
 95     {
 96     point p;
 97     cmp(const point &p0){p=p0;}
 98     bool operator()(const point &aa,point &bb)
 99     {
100         point a=aa,b=bb;
101         int d = dblcmp((a-p)^(b-p));
102         if (d==0)
103         {
104         return dblcmp(a.distance(p)-b.distance(p))<0;
105         }
106         else 
107         return d>0;
108     }
109 
110     };
111 
112     void getconvex(polygon &convex,int &top)
113     {
114     int i,j,k;
115     sort(p,p+n); //极角排序
116     convex.n=n;
117 
118     for ( int i = 0 ; i < min (n,2);i++)
119     {
120         convex.p[i] = p[i];
121     }
122     if (n<=2) return ;
123     top = convex.n;
124     top = 1;
125     for ( int i = 2 ; i < n ; i++)
126     {
127         while (top&&convex.p[top].sub(p[i]).det(convex.p[top-1].sub(p[i]))<=0) top--;
128 
129         convex.p[++top]=p[i];
130     }
131     
132        int tmp = top;
133        convex.p[++top] = p[n-2];
134        for (int i = n-3 ; i >= 0 ; i--)
135        {
136            while (top!=tmp&&convex.p[top].sub(p[i]).det(convex.p[top-1].sub(p[i]))<=0)
137            top--;
138            convex.p[++top]=p[i];
139        }
140     //   ztop = top;
141        
142     };
143 
144 }pol;
145 
146 int main()
147 {
148   #ifndef  ONLINE_JUDGE 
149    freopen("in.txt","r",stdin);
150   #endif
151 
152    while (scanf("%d %d",&n,&l)!=EOF)
153     {
154     pol.n=n;
155     pol.input();
156     polygon conv;
157     pol.getconvex(conv,top);
158     
159        double res=0;
160 //       cout<<"top:"<<top<<endl;
161        for ( int i = 0 ; i < top ; i++)
162            res +=conv.p[i].distance(conv.p[i+1]);
163        res +=conv.p[0].distance(conv.p[top]);
164 
165        res = res + 2*pi*l;
166        printf("%d\n",(int)(res+0.5));
167 
168     
169 
170     }
171   
172    
173  #ifndef ONLINE_JUDGE  
174   #endif
175   fclose(stdin);
176     return 0;
177 }