[LeetCode] Unique Word Abbreviation

Unique Word Abbreviation

An abbreviation of a word follows the form <first letter><number><last letter>. Below are some examples of word abbreviations:

a) it                      --> it    (no abbreviation)

     1
b) d|o|g                   --> d1g

              1    1  1
     1---5----0----5--8
c) i|nternationalizatio|n  --> i18n

              1
     1---5----0
d) l|ocalizatio|n          --> l10n

Assume you have a dictionary and given a word, find whether its abbreviation is unique in the dictionary. A word's abbreviation is unique if no other word from the dictionary has the same abbreviation.

Example: 

Given dictionary = [ "deer", "door", "cake", "card" ]

isUnique("dear") -> false
isUnique("cart") -> true
isUnique("cane") -> false
isUnique("make") -> true

class ValidWordAbbr {
private:
    unordered_map<string, int> m_map;
    unordered_set<string> m_set;
public:
    ValidWordAbbr(vector<string> &dictionary) {
        for (auto word : dictionary) {
            m_set.insert(word);
            if (word.length() == 2) ++m_map[word];
            else ++m_map[word.front() + to_string(word.length() - 2) + word.back()];
        }
    }

    bool isUnique(string word) {
        string key;
        if (word.length() == 2) key = word;
        else key = word.front() + to_string(word.length() - 2) + word.back();
        if (m_set.find(word) == m_set.end()) return m_map[key] < 1;
        else return m_map[key] < 2;
    }
};


// Your ValidWordAbbr object will be instantiated and called as such:
// ValidWordAbbr vwa(dictionary);
// vwa.isUnique("hello");
// vwa.isUnique("anotherWord");