Leetcode#73 Set Matrix Zeroes

原题地址

用矩形的第一行和第一列充当mask

代码：

void setZeroes(vector<vector<int> > &matrix) {
        if (matrix.empty() || matrix[0].empty()) return;
        
        bool firstRow = false;
        bool firstCol = false;
        int m = matrix.size();
        int n = matrix[0].size();
        
        for (int i = 0; i < m; i++)
            if (matrix[i][0] == 0) {
                firstCol = true;
                break;
            }
            
        for (int j = 0; j < n; j++)
            if (matrix[0][j] == 0) {
                firstRow = true;
                break;
            }
            
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (matrix[i][j] == 0) {
                    matrix[i][0] = 0;
                    matrix[0][j] = 0;
                }
            }
        }
        
        for (int i = 1; i < m; i++)
            if (matrix[i][0] == 0)
                for (int j = 1; j < n; j++)
                    matrix[i][j] = 0;
        
        for (int j = 1; j < n; j++)
            if (matrix[0][j] == 0)
                for (int i = 1; i < m; i++)
                    matrix[i][j] = 0;
        
        if (firstCol)
            for (int i = 0; i < m; i++)
                matrix[i][0] = 0;
        if (firstRow)
            for (int j = 0; j < n; j++)
                matrix[0][j] = 0;
}