分析

把x,y坐标拼接成一个字符串（x,y）作为Set的key，保存到Set中，遍历Set，取出坐标，然后判断上下左右四个点是否在Set中，如果在，进而判断，四个角是否在Set中，用一个数组，保存回收站的分数，key是（0-4），值是选址个数。

import java.util.*;

public class RecycleBin {
    public static class Pos {
        int x;
        int y;

        public int getX() {
            return x;
        }

        public void setX(int x) {
            this.x = x;
        }

        public int getY() {
            return y;
        }

        public void setY(int y) {
            this.y = y;
        }

        public Pos(int x, int y) {
            this.x = x;
            this.y = y;
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;
            Pos pos = (Pos) o;
            return x == pos.x && y == pos.y;
        }

        @Override
        public int hashCode() {
            return Objects.hash(x, y);
        }
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int num = scanner.nextInt();
        Set<Pos> set = new HashSet<>();
        int[] arr = new int[5];
        for(int i = 0; i < num; i++){
            int x = scanner.nextInt();
            int y = scanner.nextInt();
            Pos pos = new Pos(x,y);
            set.add(pos);
        }
        for(Pos pos : set){
            int x = pos.getX();
            int y = pos.getY();
            Pos pUp = new Pos(x,y+1);
            Pos pDown = new Pos(x,y-1);
            Pos pLeft = new Pos(x+1,y);
            Pos pRight = new Pos(x-1,y);

            Pos pRightUp = new Pos(x+1,y+1);
            Pos pRightDown = new Pos(x+1,y-1);
            Pos pLeftUp = new Pos(x-1,y+1);
            Pos pLeftDown = new Pos(x-1,y-1);
            if(set.contains(pUp)&&set.contains(pDown)
                    &&set.contains(pLeft) &&set.contains(pRight)){
                int count = 0;
                if(set.contains(pRightUp)){
                    count++;
                }
                if(set.contains(pRightDown)){
                    count++;
                }
                if(set.contains(pLeftUp)){
                    count++;
                }
                if(set.contains(pLeftDown)){
                    count++;
                }
                arr[count]++;
            }
        }

        for(int i : arr){
            System.out.println(i);
        }
    }
}