Radar Installation

http://poj.org/problem?id=1328

#include <cstdio>#include <cstring>#include <algorithm>#include <cmath>using namespace std;struct node{double left,right;bool operator <(const node& x)const{if(right<x.right) return 1;if(right==x.right&&left<x.left) return 1;return 0;}}a[1010];int main(int argc, char *argv[]){int k=1,n,d;while(scanf("%d%d",&n,&d)==2){if(!n&&!d) break;int x,y;int ans=-1;for(int i=0;i<n;i++){scanf("%d%d",&x,&y);//计算雷达可以处于坐标轴的范围; a[i].left=x-sqrt(d*d-y*y);a[i].right=x+sqrt(d*d-y*y);ans=max(ans,y);}printf("Case %d: ",k++);if(ans>d) printf("-1\n");else{sort(a,a+n);int ans1=1;for(int i=0,j=1;j<n;j++)if(a[j].left>a[i].right){ans1++; i=j;}printf("%d\n",ans1);}}return 0;}