poj1819Disks

 1 #include <iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<algorithm>
 5 #include<stdlib.h>
 6 #include<vector>
 7 #include<cmath>
 8 #include<queue>
 9 #include<set>
10 using namespace std;
11 #define N 1010
12 #define LL long long
13 #define INF 0xfffffff
14 const double eps = 1e-8;
15 const double pi = acos(-1.0);
16 const double inf = ~0u>>2;
17 struct point
18 {
19     double x,y,r;
20     point(double x=0,double y=0,double r =0):x(x),y(y),r(r){}
21 }p[N];
22 int o[N];
23 bool f[N];
24 typedef point pointt;
25 pointt operator -(point a,point b)
26 {
27     return point(a.x-b.x,a.y-b.y);
28 }
29 int dcmp(double x)
30 {
31     if(fabs(x)<eps) return 0;
32     return x<0?-1:1;
33 }
34 double dis(point a)
35 {
36     return sqrt(a.x*a.x+a.y*a.y);
37 }
38 int main()
39 {
40     int n,i,j;
41     while(scanf("%d",&n)!=EOF)
42     {
43         memset(f,0,sizeof(f));
44         for(i = 1; i <=  n; i++)
45         scanf("%lf",&p[i].r);
46         p[1] = point(p[1].r,0,p[1].r);
47         p[0].r = p[0].x = 0;
48         double rig;
49         for(i = 2; i <= n; i++)
50         {
51             double maxz = 0;
52             int x = i-1;
53             for(j = i-1 ; j >= 1 ; j--)
54             {
55                 double d = sqrt((p[j].r+p[i].r)*(p[j].r+p[i].r)-(p[j].r-p[i].r)*(p[j].r-p[i].r))+p[j].x;
56                 if(dcmp(d-maxz)>=0)
57                 {
58                     maxz = max(maxz,d);
59                     x = j;
60                 }
61             }
62             if(dcmp(maxz-p[i].r)<=0)
63             {
64                 p[i].x = p[i].r;
65                 for(j = 1 ; j < i; j++)
66                 f[j] = 1;
67                 continue;
68             }
69             p[i].x = maxz;
70             //cout<<i<<" "<<x<<" "<<maxz<<endl;
71             for(j = x+1 ; j < i; j++)
72             f[j] = 1;
73         }
74         int x = n;
75         for(i = 1; i <= n ;i ++)
76         {
77             if(dcmp(p[i].r+p[i].x-rig)>0)
78             {
79                 rig = max(rig,p[i].r+p[i].x);
80                 x = i;
81             }
82         }
83         for(i = x+1 ; i <= n ;i++)
84         f[i] = 1;
85         int g = 0;
86         for(i = 1; i <= n ;i++)
87         if(f[i])
88         o[++g] = i;
89         cout<<g<<endl;
90         for(i = 1; i <= g ;i++)
91         cout<<o[i]<<endl;
92     }
93     return 0;
94 }