54

class Solution {
public:
    vector<int> spiralOrder(vector<vector<int>>& m) {
        vector<int> res;
        int rows = m.size(), cols = m[0].size();
        int left=0, right=cols-1, up=0, down=rows-1;

        while(res.size() < rows*cols){
            for(int col=left; col<=right; col++)
                res.push_back(m[up][col]);

            for(int row=up+1; row<=down; row++)
                res.push_back(m[row][right]);

            if(up != down){
                for(int col=right-1; col>=left; col--)
                    res.push_back(m[down][col]);
            }

            if(left != right){
                for(int row=down-1; row>up; row--){
                    res.push_back(m[row][left]);
                }
            }
            left++; right--; up++; down--;
        }
        return res;
    }
};