poj 1328 （贪心）

#include<iostream>
#include<cmath>
#include<algorithm>
using namespace std;
int main(){
    int n,d,kase=1,r;
    double p[1005][2],island[1005][2];
    while(cin>>n>>d&&n){
        r = 0;
        for(int i=1;i<=n;i++){
            cin>>island[i][0]>>island[i][1];
        }
        for(int i=1;i<=n;i++){
            if(island[i][1]>d){
                r = -1;
                break;
            }
            else{
                double t = sqrt(d*d-island[i][1]*island[i][1]);
                p[i][0] = island[i][0]-t;
                p[i][1] = island[i][0]+t;
            }
        }
        if(r==-1){
            cout<<"Case "<<kase++<<": "<<r<<endl;
            continue;
        }
        for(int i=1;i<=n-1;i++){
            for(int j=1;j<=n-i;j++){
                if(p[j][0]>p[j+1][0]){
                    double tmp = p[j][0];
                    p[j][0] = p[j+1][0];
                    p[j+1][0] = tmp;
                    tmp = p[j][1];
                    p[j][1] = p[j+1][1];
                    p[j+1][1] = tmp;
                }
            } 
        }
        int r = 1;
        double right = p[1][1];
        for(int i=2;i<=n;i++){
            if(p[i][0]<=right){
                if(p[i][1]<right){
                    right = p[i][1];
                }
            }else{
                r++;
                right = p[i][1];
            }
        }
        cout<<"Case "<<kase++<<": "<<r<<endl;
    }
    return 0;
}