poj 1328 Radar Installation (贪心选择性质，需要抽象出来才可以)

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <string>
#include <cmath>
#include <algorithm>
#define Bug cout << "here\n";
using namespace std;
const int N = 1005;
struct node {
    double s, f;
}t[N];
bool cmp(const node a, const node b) {
    return a.f < b.f;
}
int n, d;
int main() {
    int i, x, y, ca = 0;
    while(~scanf("%d%d", &n, &d), n|d) {
        int flag = 0;
        for(i = 0; i < n; i++) {
            scanf("%d%d", &x, &y);
            if(y > d || d < 0) {
                flag = 1;
            }
            if(flag) continue;
            double ks = sqrt((double)d*d - y*y);
            t[i].s = x - ks;
            t[i].f = x + ks;
        }
        if(flag) {
            printf("Case %d: -1\n", ++ca);
            continue;
        }
        sort(t, t+n, cmp);
        int tmp = 0;
        int count = 1;
        for(i = 1; i < n; i++) {
            if(t[i].s > t[tmp].f) {
                count++;
                tmp = i;
            }
        }
        printf("Case %d: %d\n", ++ca, count);
    }
    return 0;
}