class Solution {
public:
    vector<int> printMatrix(vector<vector<int> > matrix) {
        if (matrix.empty()) {
            return matrix[0];
        }
        int row = static_cast<int>(matrix.size()) ;
        int column = static_cast<int>(matrix[0].size()) ;
        int start = 0;
        vector<int> result;
        result.clear();
         
        while (column > start*2 && row > start*2) {
            int endX = column - 1 - start;
            int endY = row - 1 - start;
            //从左到右打印一行
            for (int i=start; i<=endX; i++) {
                result.push_back(matrix[start][i]);
            }
            //从上到下打印一行
            if (start <endY) {
                for (int i=start+1; i<=endY; i++) {
                    result.push_back(matrix[i][endX]);
                }
            }
            //从右到左打印一行
            if (start < endX && start < endY) {
                for (int i=endX-1; i>=start; i--) {
                    result.push_back(matrix[endY][i]);
                }
            }
            //从下到上打印一行
            if (start<endX && start<endY-1) {
                for (int i=endY-1; i>=start+1; i--) {
                    result.push_back(matrix[i][start]);
                }
            }
            start++;
        }
        return result;
    }
};