class Solution {

public:

    vector<int> printMatrix(vector<vector<int> > matrix) {

        vector<int> ret;

        ret.clear();

        if(!matrix.empty())

        {

            int row = matrix.size();

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

            int top = 0;

            int bottom = row - 1;

            int left = 0;

            int right = col - 1;

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

            {

                for(int i = left; i <= right; i++)

                {

                    ret.push_back(matrix[top][i]);

                }

                for(int i = top + 1; i <= bottom; i++)

                {

                    ret.push_back(matrix[i][right]);

                }

                for(int i = right - 1 ; i >= left && top < bottom ; i--)    //已经打印过了的不用再打印

                {

                    ret.push_back(matrix[bottom][i]);

                }

                for(int i = bottom - 1; i > top && left < right; i--)    //已经打印过了的不用再打印

                {

                    ret.push_back(matrix[i][left]);

                }

                top++;

                right--;

                bottom--;

                left++;

            }

        }

        return ret;

    }

};