Unique Word Abbreviation

题目
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.

答案

class ValidWordAbbr {
    Map<String, Integer> map = new HashMap<>();
    Set<String> dict = new HashSet<>();
    
    public String make_abbr(String s) {
        if(s.length() <= 2) return s;
        else return s.charAt(0) + Integer.toString(s.length() - 2) + s.charAt(s.length() - 1);
    }
    
    public ValidWordAbbr(String[] dictionary) {
        for(String s : dictionary) {
            if(!dict.contains(s)) {
                String abbr = make_abbr(s);
                map.putIfAbsent(abbr, 0);
                int freq = map.get(abbr);
                map.put(abbr, freq + 1);
                dict.add(s);                
            }

        }
    }
    
    public boolean isUnique(String word) {
        Integer freq = map.get(make_abbr(word));
        if(freq == null) {
            return true;
        }
        else {
            return (freq == 1 && dict.contains(word));
        }
    }
}

/**
 * Your ValidWordAbbr object will be instantiated and called as such:
 * ValidWordAbbr obj = new ValidWordAbbr(dictionary);
 * boolean param_1 = obj.isUnique(word);
 */