POJ_Radar Installation_1328(简单贪心)

详细题解：http://www.doc88.com/p-204590908215.html

转化为区间覆盖问题

# include <stdio.h>
# include <string.h>
# include <math.h>
# include <algorithm>
using namespace std;
struct node 
{
    double l;
    double r;
}p[5012];
int comp(struct node x,struct node y)
{
    return x.l<y.l;
}
int main()
{
    int i,j,k=1,t,n,x,y;
    double d,c[5012],e[5012];
    while(scanf("%d%lf",&n,&d)!=EOF)
    {
        if(n==0 && d==0)
            break;
        int temp=1;
        for(i=0;i<n;i++)
        {
            scanf("%lf%lf",&c[i],&e[i]);
            if(abs(e[i])>d)
                temp=0;
        }
        if(d<=0 || temp==0)
            printf("Case %d: -1\n",k++);
        else
        {
            for(i=0;i<n;i++)
            {
                p[i].l=c[i]-sqrt(d*d-e[i]*e[i]);
                p[i].r=c[i]+sqrt(d*d-e[i]*e[i]);
            }    
            sort(p,p+n,comp);
            int count=1;
            double tem=p[0].r;
            for(i=1;i<n;i++)
            {
                if(p[i].r<tem)
                    tem=p[i].r;
                else if(p[i].l>tem)
                {
                    count++;
                    tem=p[i].r;
                }
            }
            printf("Case %d: %d\n",k++,count);
        }
    }
    return 0;
}