Poj1328-Radar Installation

 1 #include <cstdio>
 2 #include <iostream>
 3 #include <cmath>
 4 #include <cstdlib>
 5 using namespace std;
 6 const int MAXN = 10000 + 10;
 7 
 8 #define FFF freopen("input.txt", "r", stdin)
 9 
10 struct Node
11 {
12     double x, y;
13 } node[MAXN];
14 
15 int cmp(const void *a, const void *b)
16 {
17     return (*(Node *)a).x > (*(Node *)b).x ? 1 : -1;
18 }
19 
20 int main()
21 {
22     FFF;
23     int n;
24     double r;
25     int cas = 1;
26     while(scanf("%d %lf", &n, &r) != EOF && (n+r))
27     {
28         bool tag = false;
29         for(int i = 0; i < n; ++i)
30         {
31             scanf("%lf %lf", &node[i].x, &node[i].y);
32             if(node[i].y > r)
33             {
34                 tag = true;
35             }
36         }
37         if(tag)
38         {
39             printf("Case %d: ", cas++);
40             printf("-1\n");
41             continue;
42         }
43         ///给他进行排序，然后从一端进行扫描
44         qsort(node, n, sizeof(node[0]), cmp);
45 
46         int sum = 1;
47 
48         printf("Case %d: ", cas++);
49 
50         double left[MAXN],righ[MAXN];
51         for(int i=0 ; i < n; i++)
52         {
53             left[i] = node[i].x - sqrt(r*r - node[i].y * node[i].y);
54             righ[i] = node[i].x + sqrt(r*r - node[i].y * node[i].y);
55         }
56 
57         double temp = righ[0];
58         for(int i = 0; i < n-1; ++i)
59         {
60             if(left[i+1] > temp)
61             {
62                 temp = righ[i+1];
63                 sum++;
64             }
65             else if(righ[i+1] < temp)
66             {
67                 temp = righ[i+1];
68             }
69         }
70         printf("%d\n", sum);
71     }
72     return 0;
73 }