class Solution {
public:
vector<int> spiralOrder(vector<vector<int> > &matrix) {
if (matrix.empty() || matrix[0].empty()) return {};
int m = matrix.size(), n = matrix[0].size();
vector<int> res;
int c = m > n ? (n + 1) / 2 : (m + 1) / 2;
int p = m, q = n;
for (int i = 0; i < c; ++i, p -= 2, q -= 2) {
for (int col = i; col < i + q; ++col)
res.push_back(matrix[i][col]);
for (int row = i + 1; row < i + p; ++row)
res.push_back(matrix[row][i + q - 1]);
if (p == 1 || q == 1) break;
for (int col = i + q - 2; col >= i; --col)
res.push_back(matrix[i + p - 1][col]);
for (int row = i + p - 2; row > i; --row)
res.push_back(matrix[row][i]);
}
return res;
}
};