poj2187Beauty Contest（凸包）poj1113Wall

http://poj.org/problem?id=2187

求出形成凸包的各边 找出最大的

View Code 
 1 #include <iostream>
 2 #include<cstdio>
 3 #include<string.h>
 4 #include<algorithm>
 5 using namespace std;
 6 struct node
 7 {
 8     int x,y;
 9 }q[50011];
10 int dis(int x1,int y1,int x2,int y2)
11 {
12     return (x1-x2)*(x1-x2)+(y1-y2)*(y1-y2);
13 }
14 node st[50011];
15 bool cmp(node a,node b)
16 {
17     if((a.x-q[1].x)*(b.y-q[1].y)==(a.y-q[1].y)*(b.x-q[1].x))
18     return dis(a.x,a.y,q[1].x,q[1].y)<dis(b.x,b.y,q[1].x,q[1].y);
19     else
20     return (a.x-q[1].x)*(b.y-q[1].y)>(a.y-q[1].y)*(b.x-q[1].x);
21 }
22 int judge(node a,node b,node c)
23 {
24     if((a.x-b.x)*(c.y-a.y)-(c.x-a.x)*(a.y-b.y)>0)
25     return 1;
26     else
27     return 0;
28 }
29 int main()
30 {
31     int i,j,k =1,n,m,top =1;
32     node t;
33     scanf("%d",&n);
34     for(i = 1 ; i <= n ;i++)
35     {
36         scanf("%d%d",&q[i].x,&q[i].y);
37         if(q[i].y<q[k].y||(q[i].y==q[k].y&&q[i].x<q[k].x))
38         k = i;
39     }
40     if(k!=1)
41     {
42         t = q[1];
43         q[1] = q[k];
44         q[k] = t;
45     }
46     sort(q+2,q+n+1,cmp);
47     st[top++] = q[1];
48     st[top++] = q[2];
49     st[top++] = q[3];
50     for(i = 4; i <= n ;)
51     {
52         if(top<3||judge(st[top-1],st[top-2],q[i]))
53         {
54             st[top++] = q[i++];
55         }
56         else
57         {
58             top--;
59         }
60     }
61     int ma = 0;
62     st[top] = q[1];
63     for(i = 1 ; i < top ; i++)
64     {
65         for(j = i+1 ; j < top ; j++)
66         {
67             ma = max(ma,dis(st[i].x,st[i].y,st[j].x,st[j].y));
68         }
69     }
70     printf("%d\n",ma);
71     return 0;
72 }

http://poj.org/problem?id=1113

一样是凸包 这个总长比凸包的总长正好大了以L为半径的圆 这个看题上的那个图 很好想

直接拿上面的改一下 距离换成double 这里WA了好多次

View Code 
 1 #include <iostream>
 2 #include<cstdio>
 3 #include<string.h>
 4 #include<algorithm>
 5 #include<cmath>
 6 #define PI 3.141592653
 7 using namespace std;
 8 struct node
 9 {
10     int x,y;
11 }q[50011];
12 double dis(int x1,int y1,int x2,int y2)
13 {
14     double x = x1-x2;
15     double y = y1-y2;
16     return sqrt(x*x+y*y);
17 }
18 node st[50011];
19 bool cmp(node a,node b)
20 {
21     if((a.x-q[1].x)*(b.y-q[1].y)==(a.y-q[1].y)*(b.x-q[1].x))
22     return dis(a.x,a.y,q[1].x,q[1].y)<dis(b.x,b.y,q[1].x,q[1].y);
23     else
24     return (a.x-q[1].x)*(b.y-q[1].y)>(a.y-q[1].y)*(b.x-q[1].x);
25 }
26 int judge(node a,node b,node c)
27 {
28     if((a.x-b.x)*(c.y-a.y)-(c.x-a.x)*(a.y-b.y)>0)
29     return 1;
30     else
31     return 0;
32 }
33 int main()
34 {
35     int i,j,k =1,n,m,top =1,l;
36     node t;
37     while(scanf("%d%d",&n,&l)!=EOF)
38     {
39         top = 1;
40        for(i = 1 ; i <= n ;i++)
41         {
42             scanf("%d%d",&q[i].x,&q[i].y);
43             if(q[i].y<q[k].y||(q[i].y==q[k].y&&q[i].x<q[k].x))
44             k = i;
45         }
46         if(k!=1)
47         {
48             t = q[1];
49             q[1] = q[k];
50             q[k] = t;
51         }
52         sort(q+2,q+n+1,cmp);
53         st[top++] = q[1];
54         st[top++] = q[2];
55         st[top++] = q[3];
56         for(i = 4; i <= n ;)
57         {
58             if(top<3||judge(st[top-1],st[top-2],q[i]))
59             {
60                 st[top++] = q[i++];
61             }
62             else
63             {
64                 top--;
65             }
66         }
67         st[top] = q[1];
68         double ma;
69         ma = 2*PI*l;
70         for(i = 1 ; i < top ; i++)
71         {
72             ma += dis(st[i].x,st[i].y,st[i+1].x,st[i+1].y);
73         }
74         printf("%.0f\n",ma);
75    }
76     return 0;
77 }

 

posted @ 2012-08-16 22:36  _雨  阅读(173)  评论(0)  编辑  收藏  举报