750.cpp

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class Solution {
public:
    int countCornerRectangles(vector<vector<int>>& grid) {
        int m = grid.size(), n = grid[0].size(), res = 0;
        for (int i = 0; i < m; ++i) {
            for (int j = 0; j < n; ++j) {
                if (grid[i][j] == 0) continue;
                for (int h = 1; h < m - i; ++h) {
                    if (grid[i + h][j] == 0) continue;
                    for (int w = 1; w < n - j; ++w) {
                        if (grid[i][j + w] == 1 && grid[i + h][j + w] == 1) ++res;
                    }
                }
            }
        }
        return res;
    }
};
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class Solution {
public:
    int countCornerRectangles(vector<vector<int>>& grid) {
        int m = grid.size(), n = grid[0].size(), res = 0;
        for (int i = 0; i < m; ++i) {
            for (int j = i + 1; j < m; ++j) {
                int cnt = 0;
                for (int k = 0; k < n; ++k) {
                    if (grid[i][k] == 1 && grid[j][k] == 1) ++cnt;
                }
                res += cnt * (cnt - 1) / 2;
            }
        }
        return res;
    }
};
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