19.顺序打印矩阵

输入一个矩阵，按照从外向里以顺时针的顺序依次打印出每一个数字，例如，如果输入如下4 X 4矩阵： 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 则依次打印出数字1,2,3,4,8,12,16,15,14,13,9,5,6,7,11,10.

class Solution {
public:
    vector<int> printMatrix(vector<vector<int> > matrix) {
       vector <int> temp;
        int row = matrix.size();
        int col = matrix[0].size();
        int left = 0, top = 0, right = col - 1, bottom = row - 1;
        
        if (row == 0 || col == 0)  
            return temp;
        
        while (left <= right && top <= bottom)
        {
            //左到右
            for (int i = left; i <= right; ++i)  
                temp.push_back(matrix[top][i]);
            //上到下
            for (int i = top + 1; i <= bottom; ++i)  
                temp.push_back(matrix[i][right]);
            // 右到左
            if (top != bottom)
                for (int i = right - 1; i >= left; --i)  
                    temp.push_back(matrix[bottom][i]);
            // 下到上
            if (left != right)
                for (int i = bottom - 1; i > top; --i)  
                    temp.push_back(matrix[i][left]);
            left++,top++,right--,bottom--;
        }
        return temp;


    }
};