Coursera Algorithms week2 基础排序 练习测验: Intersection of two sets

题目原文：

Given two arrays a[] and b[], each containing n distinct 2D points in the plane, design a subquadratic algorithm to count the number of points that are contained both in array a[] and array b[].

题目的目标就是计算重复point的个数，很简单，代码如下

 import java.awt.Point;
 import java.util.Arrays;
 import java.util.HashSet;
 import java.util.Set;

 import edu.princeton.cs.algs4.StdRandom;

 public class PlanePoints {
     private Set<Point> s = new HashSet<Point>();
     private int samePointsNum;
     PlanePoints(int n,Point[] inputa, Point[] inputb){
             for(int i=0;i<n;i++){
                 s.add(inputa[i]);
                 s.add(inputb[i]);
         }
             samePointsNum = 2*n - s.size();
     }

     public int samePointsNum(){
         return samePointsNum;
     }

     public static void main(String[] args){
         int n = 10;
         Point[] a = new Point[n];
         Point[] b = new Point[n];
         System.out.println(a.length);
         for(int i=0;i<n;i++){
             a[i] = new Point();
             a[i].setLocation(StdRandom.uniform(n), StdRandom.uniform(n));
             b[i] = new Point();
             b[i].setLocation(StdRandom.uniform(n), StdRandom.uniform(n));
         }
         System.out.println(Arrays.toString(a));
         System.out.println(Arrays.toString(b));
         PlanePoints pp = new PlanePoints(n,a,b);
         System.out.println(pp.samePointsNum);
     }
 }