poj1328 Radar Installation

原题: http://poj.org/problem?id=1328

//经典区间覆盖问题 #include<iostream>#include<cstdio>#include<math.h>#include<algorithm>using namespace std;struct range{double x;double y;}r[1001];int cmp(range a,range b){return a.x<b.x;}int main(){int n,d;int c=0;scanf("%d %d",&n,&d);while(n!=0||d!=0){c++;int i;double x,y;int count=1;for(i=0;i<n;i++){scanf("%lf %lf",&x,&y);if(y>d){count=-1;}r[i].x=x-sqrt(d*d-y*y);r[i].y=x+sqrt(d*d-y*y);}sort(r,r+n,cmp);if(count!=-1){double s=r[0].y;for(i=1;i<n;i++){if(r[i].x>s){count++;s=r[i].y;}if(r[i].x<s&&r[i].y<s){s=r[i].y;}}}printf("Case %d: %d\n",c,count);scanf("%d %d",&n,&d);}}   //AC