LC 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.

从边入手，如果四个点不重合，那么形成的四条边加两个对角线只可能有两个情况，且对角线要长。

Runtime: 16 ms, faster than 57.63% of Java online submissions for Valid Square.

class Solution {
  public boolean validSquare(int[] p1, int[] p2, int[] p3, int[] p4) {
    int[][] p = {{p1[],p1[]},{p2[],p2[]},{p3[],p3[]},{p4[],p4[]}};
    int cnt = ;
    int[] len = new int[];
    for(int i=; i<; i++){
      for(int j=i+; j< ;j++){
        if(p[i][] == p[j][] && p[i][] == p[j][]) return false;
        len[cnt++] = (p[i][]-p[j][])*(p[i][]-p[j][])+(p[i][]-p[j][])*(p[i][]-p[j][]);
      }
    }
    Arrays.sort(len);
    if(len[] == len[] && len[] == len[] && len[] > len[]){
      return true;
    }
    return false;
  }
}