poj1113（Wall）

 1 //找到一个点，看是否右侧有点，有则从新找点，如果该点右侧没有点，则是凸包上的一点，每次都找到最右边的一条边
 2 
 3 #include<stdio.h>
 4 #include<algorithm>
 5 #include<string.h>
 6 #include<math.h>
 7 using namespace std;
 8 int n,sta;
 9 struct dian
10 {
11     double x;
12     double y;
13 } p[1001];
14 int cmp(dian a,dian b)
15 {
16     if(a.y==b.y)
17         return a.x<b.x;
18     return a.y<b.y;
19 }
20 double diss(int i,int j)
21 {
22     return sqrt((p[i].x-p[j].x)*(p[i].x-p[j].x)+(p[i].y-p[j].y)*(p[i].y-p[j].y));
23 }
24 int find(int ce)
25 {
26     for(int i=0; i<n; i++)
27     {
28         if (ce==sta||i==ce)
29             continue;
30         if ((p[i].x-p[sta].x)*(p[ce].y-p[sta].y)-(p[i].y-p[sta].y)*(p[ce].x-p[sta].x)>0)
31             return 2;
32     }
33     if (ce==0)
34         return 0;
35     return 1;
36 
37 }
38 int main()
39 {
40     double l;
41     while(scanf("%d%lf",&n,&l)!=EOF)
42     {
43         int i,j,vis[1001];
44         double sum=0;
45         sta=0;
46         memset(vis,0,sizeof(vis));
47         for(i=0; i<n; i++)
48             scanf("%lf%lf",&p[i].x,&p[i].y);
49         sort(p,p+n,cmp);
50         while(1)
51         {
52             for(i=0; i<n; i++)
53             {
54                 if (vis[i]||sta==i)
55                     continue;
56                 int flag=find(i);
57                 if (flag==2)
58                     continue;
59                 if (!flag)
60                 {
61                     sum+=diss(i,sta);
62                     sum+=3.14159*2*l;
63                     int sum1=sum;
64                     if(sum-0.5>=sum1)
65                         printf("%d\n",sum1+1);
66                     else
67                         printf("%d\n",sum1);
68                     return 0;
69                 }
70                 sum+=diss(i,sta);
71                 sta=i;
72                 vis[i]=1;
73             }
74         }
75     }
76     return 0;
77 }

  1 //通过建立临时凸包，判别队列前两个点和此时点是否符合要求，如果符合进队列，不符合top-1改点出队列，然后再比较队列前两个点和此时点是否符合要求，如果符合进队列....
  2 
  3 #include <algorithm>
  4 #include <iostream>
  5 #include <sstream>
  6 #include <cstdlib>
  7 #include <cstring>
  8 #include <cstdio>
  9 #include <string>
 10 #include <bitset>
 11 #include <vector>
 12 #include <queue>
 13 #include <stack>
 14 #include <cmath>
 15 #include <list>
 16 //#include <map>
 17 #include <set>
 18 using namespace std;
 19 /***************************************/
 20 #define ll long long
 21 #define int64 __int64
 22 #define PI 3.1415927
 23 /***************************************/
 24 const int INF = 0x7f7f7f7f;
 25 const double eps = 1e-8;
 26 const double PIE=acos(-1.0);
 27 const int d1x[]= {0,-1,0,1};
 28 const int d1y[]= {-1,0,1,0};
 29 const int d2x[]= {0,-1,0,1};
 30 const int d2y[]= {1,0,-1,0};
 31 const int fx[]= {-1,-1,-1,0,0,1,1,1};
 32 const int fy[]= {-1,0,1,-1,1,-1,0,1};
 33 /*vector <int>map[N];map[a].push_back(b);int len=map[v].size();*/
 34 /***************************************/
 35 void openfile()
 36 {
 37     freopen("data.in","rb",stdin);
 38     freopen("data.out","wb",stdout);
 39 }
 40 priority_queue<int> qi1;
 41 priority_queue<int, vector<int>, greater<int> >qi2;
 42 /**********************华丽丽的分割线,以上为模板部分*****************/
 43 
 44 struct node
 45 {
 46     double x,y;
 47     double angle;
 48 }p[1005];
 49 int cmp1(node a1,node a2)
 50 {
 51     if (a1.y==a2.y)
 52         return a1.x<a2.x;
 53     return a1.y<a2.y;
 54 }
 55 int cmp2(node a1,node a2)
 56 {
 57     if (a1.angle==a2.angle)
 58         return a1.x<a2.x;
 59     return a1.angle<a2.angle;
 60 }
 61 int EPS(double f)
 62 {
 63     if (fabs(f)<eps)
 64         return 0;
 65     return f>0?1:-1;
 66 }
 67 double getangle(node a1,node a2)
 68 {
 69     return atan2(a2.y-a1.y,a2.x-a1.x);
 70 }
 71 double cha(node b1,node a1)
 72 {
 73     return a1.x*b1.y-a1.y*b1.x;
 74 }
 75 double dis(node a,node b)
 76 {
 77     return sqrt((b.y-a.y)*(b.y-a.y)+(b.x-a.x)*(b.x-a.x));
 78 }
 79 int n;
 80 double r;
 81 int judge(node a,node b,node c)
 82 {
 83     int m=(a.x-b.x)*(c.y-b.y);
 84     int m1=(a.y-b.y)*(c.x-b.x);
 85     m=m-m1;
 86     if (m>0)
 87         return 1;
 88     return 0;
 89 }
 90 int main()
 91 {
 92 
 93     while(scanf("%d%lf",&n,&r)!=EOF)
 94     {
 95         int i,j;
 96         for(i=0;i<n;i++)
 97             scanf("%lf%lf",&p[i].x,&p[i].y);
 98         sort(p,p+n,cmp1);
 99         for(i=0;i<n;i++)
100             p[i].angle=getangle(p[0],p[i]);
101         sort(p,p+n,cmp2);
102         node que[1001];
103         que[0]=p[0];
104         que[1]=p[1];
105         que[2]=p[2];
106         int top=2;
107         for(i=3;i<n;i++)
108         {
109             while(top>=1&&judge(que[top-1],que[top],p[i]))
110             {
111                 top--;
112             }
113             que[++top]=p[i];
114         }
115         double sum=0;
116         for(i=0;i<top;i++)
117            sum+=dis(que[i],que[i+1]);
118         sum+=dis(que[top],que[0]);
119         sum+=2*PI*r;
120         printf("%.0lf\n",sum);
121     }
122     return 0;
123 }