54.cpp

#include <string>
#include <vector>
using namespace std;
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(), idx = 0, i = 0, j = 0;
        vector<int> res;
        vector<vector<int> > dirs{{0, 1}, {1, 0}, {0, -1}, {-1, 0}};
        for (int k = 0; k < m * n; ++k) {
            res.push_back(matrix[i][j]);
            matrix[i][j] = 0;
            int x = i + dirs[idx][0], y = j + dirs[idx][1];
            if (x < 0 || x >= m || y < 0 || y >= n || matrix[x][y] == 0) {
                idx = (idx + 1) % 4;
                x = i + dirs[idx][0];
                y = j + dirs[idx][1];
            }
            i = x;
            j = y;
        }
        return res;
    }
};