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);
    }
}