[LeetCode 593] Valid Square

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.

Example:

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

Note:

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

分析

正方形的的四个点连接起来有4条边和两条对角线，4条边的长度相等，两条对角线的长度相等，所以如果计算两两的长度只有两种结果，那么这四个点连接起来一定就是正方形。

Code

class Solution {
public:
    
    bool validSquare(vector<int>& p1, vector<int>& p2, vector<int>& p3, vector<int>& p4) {
        vector<vector<int>> p;
        p.push_back(p1);
        p.push_back(p2);
        p.push_back(p3);
        p.push_back(p4);
        
        set<int> len;
        for (int i = 0; i < 3; i ++)
        {
            for (int j = i +1; j <=3; j ++)
            {
                int diffx = p[j][0] - p[i][0];
                int diffy = p[j][1] - p[i][1];
                if (diffx == 0 && diffy == 0)
                    return false;
                len.insert(diffx * diffx + diffy * diffy);
            }
        }
        
        
        return len.size() == 2 ? true: false;
        
    }
};

运行效率

Runtime: 0 ms, faster than 100.00% of C++ online submissions for Valid Square.

Memory Usage: 8.9 MB, less than 50.28% of C++ online submissions for Valid Square.