C++ 代码

#include <cstdio>
#include <algorithm>
#include <cmath>
using namespace std;
const int N = 1010;
const double inf = 0x3f3f3f3f;
const double esp = 1e-6;
struct node{
    double l, r;
    bool operator < (const node & a) const{
        return l < a.l;
    }
}p[N];
int main(){
#ifdef ONLINE_JUDGE
#else
    freopen("in.txt", "r", stdin);
#endif //ONLINE_JUDGE
    int n, iCase = 1;
    double d, x, y;
    while(scanf("%d%lf", &n, &d)){
        bool flag = false;
        if(n == 0 && d == 0) break;
        for(int i = 0; i < n; i++){
            scanf("%lf%lf", &x, &y);
            if(y > d) flag = true;
            double len = sqrt(d * d - y * y);
            p[i] = (node){x - len, x + len};
        }
        printf("Case %d: ", iCase++);
        if(flag) printf("-1\n");
        else{
            int ans = 0;
            sort(p, p + n);
            double pos = - inf;
            for(int i = 0; i < n; i++){
                if(p[i].l > pos + esp){
                    pos = p[i].r + esp;
                    ans++;
                }
                else{
                    pos = min(pos, p[i].r);
                }
            }
            printf("%d\n", ans);
        }
    }

    return 0;
}