0054.cpp

#include <vector>
using namespace std;

class Solution {
public:
    vector<int> spiralOrder(vector<vector<int>>& matrix) {
        int l = 0, r = matrix[0].size()-1, t = 0, b = matrix.size()-1;
        vector<int> ans;

        while (l <= r && t <= b)
        {
            for (int i = l; i <= r; i++)
                ans.push_back(matrix[t][i]);
            t++;    

            for (int j = t; j <= b; j++)
                ans.push_back(matrix[j][r]);
            r--;    

            if (t <= b)
            {            
                for (int i = r; i >= l; i--)
                    ans.push_back(matrix[b][i]);
                b--;
            }
            if (l <= r)
            {
                for (int j = b; j >= t; j--)
                    ans.push_back(matrix[j][l]);
                l++;    
            }
        }
        return ans;
    }
};