leetcode 54. Spiral Matrix

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

For example,
Given the following matrix:

[
 [ 1, 2, 3 ],
 [ 4, 5, 6 ],
 [ 7, 8, 9 ]
]

class Solution {
public:
	vector<int> spiralOrder(vector<vector<int>>& matrix) {
		vector<int>re;
		if (matrix.empty() || matrix[0].empty())
			return re;
		if (matrix.size() == 1)
		{
			for (int i = 0; i < matrix[0].size(); i++)
				re.push_back(matrix[0][i]);
			return re;
		}
		if (matrix[0].size() == 1)
		{
			for (int i = 0; i < matrix.size(); i++)
				re.push_back(matrix[i][0]);
			return re;
		}
		int row = matrix.size();
		int col = matrix[0].size();
		int k = 0;
		int off = 0;
		while (true)
		{
			for (int i = off; i < col - off; i++)
			{
				re.push_back(matrix[off][i]); k++;
			}
			if (k == row*col )
				return re;
			for (int i = off + 1; i < row - off; i++)
			{
				re.push_back(matrix[i][col - 1 - off]); k++;
			}
			if (k == row*col)
				return re;
			for (int i = col - 2 - off; i >= off; i--)
			{
				re.push_back(matrix[row - 1 - off][i]);  k++;
			}
			if (k == row*col)
				return re;
			for (int i = row - 2 - off; i >= off + 1; i--)
			{
				re.push_back(matrix[i][off]); k++;
			}
			if (k == row*col)
				return re;
			off++;
		}
	}
};

accepted