973. K Closest Points to Origin (PriorityQueue && Comparator)

这是一段如何：

1. 新建class数据结构
2. 复写PriorityQueue的Comparator
3. 如何新建int array并赋值
   的演示代码；
   Java 默认 PriorityQueue 会将最小的值pop，复写Comparator的时候在A>B时return -1就可以让PriorityQueue每次pop出最大的值，符合本题的需求

import java.util.*;

class priorityQ {
    public int[][] kClosest(int[][] points, int K) {
        int length = points.length;
        if(length <= K){return points;}
        PriorityQueue<Point> queue = new PriorityQueue<>(new PointComparator());
        for(int i = 0; i < length; i++){
            Point tmp = new Point(points[i]);
            queue.add(tmp);
            while(queue.size() > K){
                queue.poll();
            }
        }
        int[][] ans = new int[K][2];
        for(int j = 0; j < K; j++){
            ans[j] = queue.poll().reformat();
        }
        return ans;
    }


    class Point{
        private int x;
        private int y;
        private int distance;
        private int[] point;

        Point(int[] point){
            this.x = point[0];
            this.y = point[1];
            this.distance = this.x * this.x + this.y * this.y;
            this.point = point;
        }

        int distance(){
            return this.distance;
        }

        int[] reformat(){
            return this.point;
        }
    }

    class PointComparator implements Comparator<Point>{
        public int compare(Point point1, Point point2){
            if(point1.distance > point2.distance){
                return -1;
            }
            else if(point1.distance < point2.distance){
                return 1;
            }
            else{
                return 0;
            }
        }
    }

    public static void main(String[] args){
        int[][] points = {{-1,3},{2,2},{5,7},{6,6}};
        priorityQ qQ = new priorityQ();
        int[][] reply = qQ.kClosest(points, 2);
        for(int[] tmp : reply){
            System.out.println(Arrays.toString(tmp));
        }
    }
}