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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:

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.

本题的主要思路是判断四条边是否相等，两条对角线是否相等。

int squre_dis(vector
   
    & p1, vector
    
     & p2){    return pow(p1[0] - p2[0], 2) + pow(p1[1] - p2[1], 2);}bool validSquare(vector
     
      & p1, vector
      
       & p2, vector
       
        & p3, vector
        
         & p4) { int d1 = squre_dis(p1, p2), d2 = squre_dis(p1, p3), d3 = squre_dis(p1, p4), d4 = squre_dis(p2, p3), d5 = squre_dis(p2, p4), d6 = squre_dis(p3, p4); if (d1 == 0 || d2 == 0 || d3 == 0 || d4 == 0 || d5 == 0 || d6 == 0) return false; set
         
           res; res.insert(d1), res.insert(d2), res.insert(d3), res.insert(d4), res.insert(d5), res.insert(d6); if (res.size() == 2)return true; return false;}
         
        
       
      
     
    
   

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