leetcode593+判断四个点是不是组成了正方形，看所有点的距离是不是只有两种

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https://leetcode.com/problems/valid-square/description/

class Solution {
public:
    bool validSquare(vector<int>& p1, vector<int>& p2, vector<int>& p3, vector<int>& p4) {
        map<int, int> Mp;
        vector<vector<int>> all{p1, p2, p3, p4};
        for(int i=0; i<all.size(); i++){
            for(int j=i+1; j<all.size(); j++){
                int x1 = all[i][0], y1 = all[i][1], x2=all[j][0], y2=all[j][1];
                int len = (x1-x2)*(x1-x2)+(y1-y2)*(y1-y2);
                if(len==0) return false;
                Mp[len] +=1;
            }
        }
        return Mp.size()==2;
    }
};