C++ top-down and bottom-up


  • 0

    Top-down version of this post.

    class Solution {
    public:
        void setZeroes(vector<vector<int>>& matrix) {
            if(matrix.empty()) return;
            int m = matrix.size(), n = matrix[0].size(), col0 = 1;
            for(int i = 0; i < m; i++){
                if(!matrix[i][0]) col0 = 0;
                for(int j = 1; j < n; j++)
                    if(!matrix[i][j]) matrix[0][j] = matrix[i][0] = 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(!col0) matrix[i][0] = 0;
            }
            for(auto& x: matrix[0]) if(!matrix[0][0]) x = 0;
            if(!col0) matrix[0][0] = 0;
        }
    };
    

    And bottom-up.

    class Solution {
    public:
        void setZeroes(vector<vector<int>>& matrix) {
            if(matrix.empty()) return;
            int m = matrix.size(), n = matrix[0].size(), col0 = 1;
            for(int i = 0; i < m; i++){
                if(!matrix[i][0]) col0 = 0;
                for(int j = 1; j < n; j++)
                    if(!matrix[i][j]) matrix[0][j] = matrix[i][0] = 0;
            }
            
            for(int i = m - 1; i >= 0; i--){
                for(int j = n - 1; j > 0; j--)
                    if(!matrix[i][0] || !matrix[0][j]) matrix[i][j] = 0;
                if(!col0) matrix[i][0] = 0;
            }
        }
    };
    

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