Переводчик

#include <cassert>
#include <iostream>
#include <string_view>
#include <algorithm>
#include <map>
#include <set>

using namespace std;

class Translator {
public:
    Translator() = default;

    void Add(string_view source, string_view target) {
        all_words_.insert(string{ source });
        all_words_.insert(string{ target });

        first_to_second_lang_[*all_words_.find(string{ source })] = *all_words_.find(string{ target });
        second_to_first_lang_[*all_words_.find(string{ target })] = *all_words_.find(string{ source });
    }
    string_view TranslateForward(string_view source) const {
        if (first_to_second_lang_.count(source)) {
            return first_to_second_lang_.at(source);
        }
        return "";
    }
    string_view TranslateBackward(string_view target) const {
        if (second_to_first_lang_.count(target)) {
            return second_to_first_lang_.at(target);
        }
        return "";
    }

private:
    map<string_view, string_view> first_to_second_lang_;
    map<string_view, string_view> second_to_first_lang_;
    set<string> all_words_;
};

void TestSimple() {
    Translator translator;
    translator.Add(string("okno"s), string("window"s));
    translator.Add(string("stol"s), string("table"s));

    assert(translator.TranslateForward("okno"s) == "window"s);
    assert(translator.TranslateBackward("table"s) == "stol"s);
    assert(translator.TranslateForward("table"s) == ""s);
}

int main() {
    TestSimple();
    return 0;
}