POJ 1328 Radar Installation

 1 #include<iostream>
 2 #include<algorithm>
 3 #include<cmath>
 4 using namespace std;
 5 struct Location
 6 {
 7     double x;double y;
 8 };
 9 struct Section
10 {
11     double x1;double x2;
12 };
13 const int MAX_N=1000;
14 Location Loc[MAX_N];
15 Section Sec[MAX_N];
16 int results[MAX_N];
17 int N,D;
18 //计算每个点所对应的区间 ，注意section b需要计算，函数参数前不能加const 
19 void calculate(const Location& a, Section& b)
20 {
21     double temp = sqrt(D*D-a.y*a.y);
22     b.x1 = temp+a.x;
23     b.x2 = a.x-temp;
24     return ;
25 }
26 //用end排序 
27 bool is_greater(const Section& a,const Section& b)
28 {
29     return (a.x1<b.x1)||(a.x1==b.x1 && a.x2<=b.x2);
30 }
31 int solve()
32 {
33     //检查是否有解 
34     bool found=false;
35     int i;
36     for(i=0;i<N;i++)
37     {
38         if(Loc[i].y>D)
39         {
40             found=true;
41             break;
42         }
43     }
44     if(found)
45     {
46         return -1;
47     }
48     for(i=0;i<N;i++)
49     {
50         calculate(Loc[i],Sec[i]);
51     }
52     sort(Sec,Sec+N,is_greater);
53     int k=0;
54     int q=0;
55     int num=0;
56     while(k<N)
57     {
58         k=q+1;
59         //判断end是否在下个区间里 
60         while(Sec[q].x1>=Sec[k].x2 && Sec[q].x1<=Sec[k].x1 && k<N)
61         {
62             k++;
63         }
64         q=k;
65         num++;
66     }
67     return num;
68 }
69 int main()
70 {
71     int times=0;
72     while(cin>>N>>D,N||D)
73     {
74         int i=0;
75         for(;i<N;i++)
76         {
77             cin>>Loc[i].x>>Loc[i].y;
78         }
79         results[times]=solve();
80         times++;
81     }
82     for(int l=0;l<times;l++)
83     {
84         cout<<"Case "<<l+1<<": "<<results[l]<<endl;
85     }
86     return 0;
87 }