1. Description

Given the coordinates of four points in 2D space, return whether the four points could construct a square.

The coordinate (x,y) of a point is represented by an integer array with two integers.

All the input integers are in the range [-10000, 10000].
A valid square has four equal sides with positive length and four equal angles (90-degree angles).
Input points have no order.

2. Runtime Distribution

3. Submission Details

4. Example

Input: p1 = [0,0], p2 = [1,1], p3 = [1,0], p4 = [0,1]
Output: True

So the maximum integer in M is 2, and there are four of it in M. So return 4.

5. Code

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public boolean validSquare(int[] p1, int[] p2, int[] p3, int[] p4) {

	Map map = new HashMap();
	map.put(distance(p1, p2), 1);

	double tmp = distance(p1, p3);
	map.put(tmp, map.getOrDefault(tmp, 0) + 1);

	tmp = distance(p1, p4);
	map.put(tmp, map.getOrDefault(tmp, 0) + 1);

	tmp = distance(p2, p3);
	map.put(tmp, map.getOrDefault(tmp, 0) + 1);

	tmp = distance(p2, p4);
	map.put(tmp, map.getOrDefault(tmp, 0) + 1);

	tmp = distance(p3, p4);
	map.put(tmp, map.getOrDefault(tmp, 0) + 1);

	return !map.containsKey(0.0) && map.values().size() == 2 && map.values().contains(4)
			&& map.values().contains(2);
}

private double distance(int[] a, int[] b) {
	int diffX = a[0] - b[0];
	int diffY = a[1] - b[1];
	return Math.sqrt(diffX * diffX + diffY * diffY);
}

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6.Test

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import java.util.HashMap;
import java.util.Map;

public class LeetCode0593 {

	public boolean validSquare(int[] p1, int[] p2, int[] p3, int[] p4) {

		Map map = new HashMap();
		map.put(distance(p1, p2), 1);

		double tmp = distance(p1, p3);
		map.put(tmp, map.getOrDefault(tmp, 0) + 1);

		tmp = distance(p1, p4);
		map.put(tmp, map.getOrDefault(tmp, 0) + 1);

		tmp = distance(p2, p3);
		map.put(tmp, map.getOrDefault(tmp, 0) + 1);

		tmp = distance(p2, p4);
		map.put(tmp, map.getOrDefault(tmp, 0) + 1);

		tmp = distance(p3, p4);
		map.put(tmp, map.getOrDefault(tmp, 0) + 1);

		return !map.containsKey(0.0) && map.values().size() == 2 && map.values().contains(4)
				&& map.values().contains(2);
	}

	private double distance(int[] a, int[] b) {
		int diffX = a[0] - b[0];
		int diffY = a[1] - b[1];
		return Math.sqrt(diffX * diffX + diffY * diffY);
	}

	public static void main(String[] args) {
		int[] p1 = new int[] { 1, 0 };
		int[] p2 = new int[] { -1, 0 };
		int[] p3 = new int[] { 0, 1 };
		int[] p4 = new int[] { 0, -1 };

		LeetCode0593 leetcode = new LeetCode0593();
		System.out.println(leetcode.validSquare(p1, p2, p3, p4));
	}
}

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