POJ1328 Radar Installation

 1 #include <iostream>
 2 #include <iostream>
 3 #include <cstdio>
 4 #include <cstdlib>
 5 #include <string>
 6 #include <algorithm>
 7 #include <cmath>
 8 #define min(a, b) ((a) < (b) ? (a) : (b))
 9 
10 const int INF = 0x7fffffff;
11 const int MAXN = 1000 + 10;
12 
13 inline void read(int &x)
14 {
15     x = 0;char ch = getchar(),c = ch;
16     while(ch < ‘0‘ || ch > ‘9‘)c = ch, ch = getchar();
17     while(ch <= ‘9‘ && ch >= ‘0‘)x = x * 10 + ch - ‘0‘, ch = getchar();
18     if(c == ‘-‘)x = -x;
19 }
20 
21 int n, R, cnt[MAXN], ans, t, ok;
22 double l[MAXN], r[MAXN], now;
23 
24 bool cmp(int a, int b)
25 {
26     return l[a] < l[b];
27 }
28 
29 int main()
30 {
31     while(scanf("%d%d", &n, &R) && (n + R))
32     {
33         ans = now = ok = 0;
34         register int x,y;
35         for(register int i = 1;i <= n;++i)
36         {
37             cnt[i] = i;
38             read(x);read(y);
39             if(R < y) ans = -1,ok = 1;
40             double tmp = sqrt(R * R - y * y);
41             l[i] = x - tmp;
42             r[i] = x + tmp;
43         }
44         if(ok)goto L1;
45         std::sort(cnt + 1, cnt + 1 + n, cmp);
46         now = -INF;
47         for(register int i = 1;i <= n;++ i)
48             if(l[cnt[i]] > now) ans ++, now = r[cnt[i]];
49             else now = min(now, r[cnt[i]]);
50 L1:        ;
51         if(!ans) ans = -1;
52         printf("Case %d: %d\n", ++t, ans);
53     } 
54     return 0;
55 }