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.
思路：
4个点，求出任意两点之间的距离，总共6条线段，存在其中4条相等，而且另外两条也相等就是正方形。
double length(vector<int>& p1, vector<int>& p2)
{
int x = abs(p1[] - p2[]);
int y = abs(p1[] - p2[]);
return x*x + y*y;
}
bool validSquare(vector<int>& p1, vector<int>& p2, vector<int>& p3, vector<int>& p4)
{
map<double,int>table;
table[length(p1,p2)]++;
table[length(p1,p3)]++;
table[length(p1,p4)]++;
table[length(p2,p3)]++;
table[length(p2,p4)]++;
table[length(p3,p4)]++;
if(table.size()!=) return false; map<double ,int>::iterator it = table.begin();
map<double ,int>::iterator temp = it;
temp++;
if((it->second == && temp->second == ) ||(it->second == && temp->second ==) )return true;
return false;
}
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