poj 1819 Disks

http://poj.org/problem?id=1819

 1 #include <cstdio>

 2 #include <cstring>

 3 #include <cmath>

 4 #include <cstdlib>

 5 #include <algorithm>

 6 using namespace std;

 7 

 8 const double eps=1e-8;

 9 struct point

10 {

11     double x;

12     double y,r;

13 }pp[2000];

14 bool flag[2000];

15 int stack1[2000],n;

16 

17 int main()

18 {

19     while(scanf("%d",&n)!=EOF)

20     {

21         double x;

22         int p=0,i,last;

23         for(last=i=1; i<=n; i++){

24             flag[i]=true;

25             scanf("%lf",&pp[i].r);

26             int k=0;

27             pp[i].x=pp[i].y=pp[i].r;

28             for(int j=1; j<=p; j++)

29             {

30                 x=pp[stack1[j]].x+2*sqrt(pp[i].r*pp[stack1[j]].r);

31                 if(x-pp[i].x>eps)

32                 {

33                     pp[i].x=x;

34                     k=j;

35                 }

36             }

37             p=k;

38             stack1[++p]=i;

39             if(pp[i].x+pp[i].r-pp[last].x-pp[last].r>eps)

40             {

41                 last=i;

42             }

43         }

44         for(int i=1; i<=p; i++) flag[stack1[i]]=0;

45         for(int j=last+1; j<=n; j++)

46         {

47             flag[j]=true;

48         }

49         int num=0;

50         for(int i=1; i<=n; i++)

51         {

52             if(flag[i])

53             {

54                 num++;

55             }

56         }

57         printf("%d\n",num);

58         for(int i=1; i<=n; i++)

59         {

60             if(flag[i])

61             {

62                 printf("%d\n",i);

63             }

64         }

65     }

66     return 0;

67 }

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