顺时针打印矩阵

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

        vector<int> res;
        res.clear();
        int row=matrix.size();
        int col=matrix[0].size();
        if(row==0||col==0) return res;

        int top=0,bottom=row-1,left=0,right=col-1;
        while(top<=bottom&&left<=right)
        {
            for(int i=left;i<=right;++i) 
            {
                res.push_back(matrix[top][i]);
            }
            for(int i=top+1;i<=bottom;++i)
            {
                res.push_back(matrix[i][right]);
            }
           if(top!=bottom)
            for(int i=right-1;i>=left;--i)
            {
                res.push_back(matrix[bottom][i]);
            }
           if(left!=right)
            for(int i=bottom-1;i>top;--i)
            {
                res.push_back(matrix[i][left]);
            }

            left++;
            right--;
            top++;
            bottom--;
        }
        return res;
    }
};