2022.7.26

class Solution { 
        public:     int projectionArea(vector<vector<int>>& grid) { 
                  int n = grid.size();         int xyArea = 0, yzArea = 0, zxArea = 0;         for (int i = 0; i < n; i ) { 
                    int yzHeight = 0, zxHeight = 0;             for (int j = 0; j < n; j ) { 
                        xyArea  = grid[i][j] > 0 ? 1 : 0;                 yzHeight = max(yzHeight, grid[j][i]);                 zxHeight = max(zxHeight, grid[i][j]);             }             yzArea  = yzHeight;             zxArea  = zxHeight;         }         return xyArea   yzArea   zxArea;     } };

class Solution { 
       
public:
    int minimumLines(vector<vector<int>>& stockPrices) { 
       
        sort(stockPrices.begin(), stockPrices.end());
        int n = stockPrices.size();
        if (n <= 2) { 
       
            return n - 1;
        }
        int res = 1;
        for (int i = 2; i < n; ++i) { 
       
            long long dx0 = stockPrices[i-1][0] - stockPrices[i-2][0];
            long long dy0 = stockPrices[i-1][1] - stockPrices[i-2][1];
            long long dx1 = stockPrices[i][0] - stockPrices[i-1][0];
            long long dy1 = stockPrices[i][1] - stockPrices[i-1][1];
            if (dx0 * dy1 != dy0 * dx1) { 
       
                ++res;
            }
        }
        return res;
    }
};

class Solution { 
       
public:
    int GetLenSquare(vector<int> point1, vector<int> point2) { 
       
       return (point2[0] - point1[0]) * (point2[0] - point1[0]) + (point2[1] - point1[1]) * (point2[1] - point1[1]);
    }

    bool validSquare(vector<int>& p1, vector<int>& p2, vector<int>& p3, vector<int>& p4) { 
       
        unordered_set<int> set = 
        { 
       
            GetLenSquare(p1, p2),
            GetLenSquare(p1, p3),
            GetLenSquare(p1, p4),
            GetLenSquare(p2, p3),
            GetLenSquare(p2, p4),
            GetLenSquare(p3, p4)
        };

        if (set.find(0) == set.end() && set.size() == 2)  
        { 
       
            return true;
        }

        return false;
    }
};