288. Unique Word Abbreviation

The abbreviation of a word is a concatenation of its first letter, the number of characters between the first and last letter, and its last letter. If a word has only two characters, then it is an abbreviation of itself.

For example:

• dog —> d1g because there is one letter between the first letter ‘d’ and the last letter ‘g’.
• internationalization —> i18n because there are 18 letters between the first letter ‘i’ and the last letter ‘n’.
• it —> it because any word with only two characters is an abbreviation of itself.

Implement the ValidWordAbbr class:

• ValidWordAbbr(String[] dictionary) Initializes the object with a dictionary of words.
• boolean isUnique(string word) Returns true if either of the following conditions are met (otherwise returns false):
  • There is no word in dictionary whose abbreviation is equal to word’s abbreviation.
  • For any word in dictionary whose abbreviation is equal to word’s abbreviation, that word and word are the same.

class ValidWordAbbr {
private:
    unordered_map<string, set<string>> words;

private:
    string getAbbreviation(string word) {
        return word.length() <= 2 ? word : word[0] + to_string(word.length() - 2) + word[word.length() - 1];
    }
public:
    ValidWordAbbr(vector<string>& dictionary) {
        for(string word : dictionary) {
            string abbreviation = getAbbreviation(word);
            auto it = words.find(abbreviation);
            if(it == words.end()) {
                words.insert(make_pair(abbreviation, set<string> {word}));
            } else {
                it->second.insert(word);
            }
        }
    }

    bool isUnique(string word) {
        auto it = words.find(getAbbreviation(word));
        return it == words.end() || (*(it->second.begin()) == word && it->second.size() == 1);
    }
};