LeetCode 73. Set Matrix Zeroes

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class Solution {
public:
    void setZeroes(vector<vector<int>>& matrix) {
        int m = matrix.size();
        int n = matrix[0].size();
        vector<int> row(m), col(n);
        for (int i = 0; i < m; i++)
            for (int j = 0; j < n; j++)
                if (!matrix[i][j])
                    row[i] = col[j] = true;
        for (int i = 0; i < m; i++)
            for (int j = 0; j < n; j++)
                if (row[i] || col[j])
                    matrix[i][j] = 0;
    }
};
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class Solution {
public:
    void setZeroes(vector<vector<int>>& matrix) {
        int m = matrix.size();
        int n = matrix[0].size();
        int flag_col0 = false, flag_row0 = false;
        for (int i = 0; i < m; i++)
            if (!matrix[i][0])
                flag_col0 = true;
        for (int j = 0; j < n; j++)
            if (!matrix[0][j])
                flag_row0 = true;
        for (int i = 1; i < m; i++)
            for (int j = 1; j < n; j++)
                if (!matrix[i][j])
                    matrix[i][0] = matrix[0][j] = 0;
        for (int i = 1; i < m; i++)
            for (int j = 1; j < n; j++)
                if (!matrix[i][0] || !matrix[0][j])
                    matrix[i][j] = 0;
        if (flag_col0)
            for (int i = 0; i < m; i++)
                matrix[i][0] = 0;
        if (flag_row0)
            for (int j = 0; j < n; j++)
                matrix[0][j] = 0;
    }
};
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class Solution {
public:
    void setZeroes(vector<vector<int>>& matrix) {
        int m = matrix.size();
        int n = matrix[0].size();
        int flag_col0 = false;
        for (int i = 0; i < m; i++) {
            if (!matrix[i][0])
                flag_col0 = true;
            for (int j = 1; j < n; j++)
                if (!matrix[i][j])
                    matrix[i][0] = matrix[0][j] = 0;
        }
        for (int i = m - 1; i >= 0; i--) {
            for (int j = 1; j < n; j++)
                if (!matrix[i][0] || !matrix[0][j])
                    matrix[i][j] = 0;
            if (flag_col0)
                matrix[i][0] = 0;
        }
    }
};