Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.

Example 1:

Input:
[
[ 1, 2, 3 ],
[ 4, 5, 6 ],
[ 7, 8, 9 ]
]
Output: [1,2,3,6,9,8,7,4,5]
Example 2:

Input:
[
[1, 2, 3, 4],
[5, 6, 7, 8],
[9,10,11,12]
]
Output: [1,2,3,4,8,12,11,10,9,5,6,7]

C++vector<int> spiralOrder(vector<vector<int>>& matrix) {
        vector<int> res;
        if(matrix.size() == 0||matrix[0].size() == 0)
            return res;
        int width = matrix[0].size();
        int height = matrix.size();
        int left = 0;
        int right = width - 1;
        int top = 0;
        int bottom = height - 1;
        while(true)
        {
            for(int i = left;i <= right;++i)
            {
                res.push_back(matrix[top][i]);
            }
            ++top;
            if(top > bottom)
                break;
            for(int i = top;i <= bottom;++i)
            {
                res.push_back(matrix[i][right]);
            }
            --right;
            if(left >right)
                break;
            for(int i = right;i >= left;--i)
            {
                res.push_back(matrix[bottom][i]);
            }
            --bottom;
            if(bottom < top)
                break;
            for(int i = bottom;i >= top;--i)
            {
                res.push_back(matrix[i][left]);
            }
            ++left;
            if(left > right)
                break;
        }
        return res;
    }