class Solution {
public:
    vector<int> spiralOrder(vector<vector<int> > &matrix) {

        vector<int> result;

        int row = matrix.size();

        if( row == 0 ) {
            return result;
        }

        int col = matrix[0].size();

        if( row == 0 && col == 0 ) {
            return result;
        }

        if( row == 1 && col == 1 ) {
            result.push_back(matrix[0][0]);
            return result;
        }

        int left = 0, right = col;
        int top = 0, bottom = row;


        while(top < bottom && left < right) {

            if( top < bottom ) {
                for( int i = left; i < right ; i++ ) {
                    result.push_back(matrix[top][i]);
                }
                top++;
            }

            if( left < right ) {
                for( int i = top; i < bottom; i++) {
                    result.push_back(matrix[i][right-1]);
                }
                right--;
            }

            if( top < bottom ) {
                for( int i = right - 1; i >= left ; i-- ) {
                    result.push_back(matrix[bottom-1][i]);
                }
                bottom--;
            }

            if( left < right ) {
                for( int i = bottom - 1 ; i >= top ; i-- ) {
                    result.push_back(matrix[i][left]);
                }
                left++;
            }

        }

        return result;

    }
};