Directions Reduction

• Time : $O(n)$
• Space : $O(n)$

using namespace std;
class DirReduction
{
public:
    static std::vector<std::string> dirReduc(std::vector<std::string> &arr) {
        unordered_map<string, string> appo;
        appo["NORTH"] = "SOUTH";
        appo["SOUTH"] = "NORTH";
        appo["EAST"] = "WEST";
        appo["WEST"] = "EAST";
        vector<string> res;
        for(auto d : arr) {
            if(res.size() and res.back() == appo[d]) res.pop_back();
            else res.push_back(d);
        }
        return res;
    }
};