Poj Solution 1328

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

import java.io.PrintWriter;  

 import java.util.Arrays;  
 import java.util.Scanner;  
 /**  
  *  
  * @author 小e  
  *  
  * 2010-6-12 下午01:48:35  
  */ 
 public class Main {  
  static class Range implements Comparable<Range>{  
   double left,right;  
   public Range(double left,double right){  
    this.left = left;  

   this.right = right;  
   }  
   @Override 

   public int compareTo(Range range) {  
    if(range.left == left){  
     return ((Double)right).compareTo((Double)(range.right));  
    }else{  
    return ((Double)left).compareTo((Double)(range.left));  
    }  
   }  

   @Override 
   public String toString() {  
    return "(" + left + "," + right + ")";  
   }  
  }  

     
  public static void main(String[] args) {  
   Scanner scn = new Scanner(System.in);    
   
   PrintWriter out = new PrintWriter(System.out);  
   int n ,d,x,y,num;  
   double dx;  
   Range[] ranges;  
   int index = 0;  
   while(true){  
    num = 0;  
    n = scn.nextInt();  
    d = scn.nextInt();  
    if(n == 0){  
     break;  
    }  
    ranges = new Range[n];  
    for(int i = 0; i < n; i++){  
     x = scn.nextInt();  
     y = scn.nextInt();  
     if(y > d){  
      num = -1;  
     }  
     dx = Math.sqrt(d*d - y*y);  
     ranges[i] = new Range(x - dx, x + dx);  
    }  
    Arrays.sort(ranges);//排序  
    if(num != -1){  
     num = calute(ranges);  
    }  
    out.format("Case %d: %dn",++index,num);  
   }  
   out.flush();  
      
  }  
    
  private static int calute(Range[] ranges) {  
   int num = 1;  
   int n = ranges.length;  
   Range preRange = ranges[0],range;  
   for(int i = 1; i < n; i++){  
    range = ranges[i];  
    //求区间交集  
    if(range.left >= preRange.left && range.left <= preRange.right){  
     preRange.left = range.left;  
     if(range.right < preRange.right){  
      preRange.right = range.right;  
     }  
    }else{  
     num++;  
     preRange = range;  
    }  
   }  
   return num;  
  }  
}