贪心- Radar Installation POJ

贪心+预处理

有个点 就是写错了，找了半天哇。 R是double类型不是int类型！

#include <iostream>
#include <cstdio>
#include <cstring>
#include <limits> 
#include<cmath>
#include <algorithm>
#define endl '
'
#define _for(i,a,b) for(int i=a;i<b;i++)
using namespace std;
const int N = 1e4+5;
typedef long long ll;
int n,d; 
struct Node{
    double l,r;
    bool operator < ( const Node &o )const{
        if( l!=o.l )
            return l<o.l;
        return r<o.r;
    }
}a[N]; 
int main(){
    ios::sync_with_stdio(0),cin.tie(0),cout.tie(0); 
    int Case = 1;
    while(cin>>n>>d){
        int flag = 0;
        if( n+d==0 ) break;
        _for(i,0,n){
            int x,y; cin>>x>>y;
            if( flag  ) continue;
            if( abs(y)>d ){
                flag = 1; continue;
            }
            double py = sqrt( d*d - y*y );
            a[i].l = x-py,a[i].r = x+py;
        }
        if( flag ){
            cout<<"Case "<<Case++<<": "<<-1<<endl;
            continue; 
        }
        sort( a,a+n );
        double R = a[0].r; int cnt = 1;
        _for(i,1,n){
            if( a[i].r < R ) R = a[i].r;
            else if( a[i].l > R ){
                cnt++;
                R = a[i].r;
            }
        } 
        
        cout<<"Case "<<Case++<<": "<<cnt<<endl;
    }
    return 0;
}