POJ - 1328(贪心）

版权声明：仅供研究，转载请注明出处。 https://blog.csdn.net/CSUstudent007/article/details/83904709

#include<cmath>
#include<algorithm>
#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;
struct Interval{
	double left;
	double right;
};
bool compare(Interval a,Interval b){
	return a.left<=b.left;
} 
int solve(Interval * intervals,int size){
	sort(intervals,intervals+size,compare);
	int minPoint=1;
	double right=intervals[0].right;
	for(int i=1;i<size;i++){
		if(intervals[i].left>right){
			minPoint++;
			right=intervals[i].right;
		}
		else if(intervals[i].right<right){
			right=intervals[i].right;
		}
	}
	return minPoint;
}
int main(){
	int island,radius,t;
	while((cin>>island>>radius)&&island&&radius){
		const double R2=radius*radius;
		Interval* intervals=new Interval[island];
		bool isSolvable=true;
		for(int i=0;i<island;i++){
			double x,y;
			cin>>x>>y;
			if(y>radius){
				isSolvable=false;
			}
			double offset=sqrt(R2-y*y);
			intervals[i].left=x-offset;
			intervals[i].right=x+offset;
		}
		int minRadar=(isSolvable?solve(intervals,island):-1);
		cout<<"Case "<<++t<<": "<<minRadar<<endl;
		delete[] intervals;
	}
	return 0;
}