正方形(类)

Problem Description

给出四个点，判断这四个点能否构成一个正方形。

Input

 输入的第一行包含一个整数T（T≤30）表示数据组数，每组数据只有一行，包括8个整数x1, y1, x2, y2，x3，y3，x4，y4（数据均在-1000,1000 之间）以逆时针顺序给出四个点的坐标。

Output

 每组数据输出一行，如果是正方形，则输出： YES， 否则，输出：NO。

Sample Input

2

0 0 1 0 1 1 0 1

-1 0 0 -2 1 0 2 0

Sample Output

YES

NO

import java.util.Scanner;
class Point {
	int x;
	int y;
	
	public Point(int x, int y) {
		this.x = x;
		this.y = y;
	}
	
	public int dist(Point p) {
		int t = (x-p.x)*(x-p.x)+(y-p.y)*(y-p.y);
		return t;
	}
	
}
public class Main {

	public static void main(String[] args) {
		Scanner reader = new Scanner(System.in);  
		int n = reader.nextInt();
		for(int i=0; i<n; i++){
			int x1 = reader.nextInt();  
            int y1 = reader.nextInt();  
            int x2 = reader.nextInt();  
            int y2 = reader.nextInt();  
            int x3 = reader.nextInt();  
            int y3 = reader.nextInt();  
            int x4 = reader.nextInt();  
            int y4 = reader.nextInt();
            Point p1 = new Point(x1, y1);
            Point p2 = new Point(x2, y2);  
            Point p3 = new Point(x3, y3);  
            Point p4 = new Point(x4, y4);  
            int dis1 = p1.dist(p2);  
            int dis2 = p2.dist(p3);  
            int dis3 = p3.dist(p4);  
            int dis4 = p4.dist(p1);  
            int m1 = p1.dist(p3);
            if (dis1 == dis2 && dis2 == dis3 && dis3 == dis4  
                    && (dis1 + dis2 == m1))  
                System.out.println("YES");  
            else  
                System.out.println("NO"); 
		}
	}

}