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") -> [code]false

isUnique("cart") ->

true

isUnique("cane") ->

false

isUnique("make") ->

true

思路： 用hashmap统计brave，生成<K,V> --> <String, HashSet<String>>，然后判断word的hashset里面是否只有一个跟word本身相等的string，如果是return true，otherwise return false。

public class ValidWordAbbr {

    HashMap<String, HashSet<String>> hashmap = new HashMap<String, HashSet<String>>();
    public ValidWordAbbr(String[] dictionary) {
        for(int i=0; i<dictionary.length; i++){
            String key = generateKey(dictionary[i]);
            if(hashmap.containsKey(key)){
                hashmap.get(key).add(dictionary[i]);
            } else {
                HashSet<String> hashset = new HashSet<String>();
                hashset.add(dictionary[i]);
                hashmap.put(key, hashset);
            }
        }
    }
    
    public String generateKey(String str){
        if(str.length() == 0) return str;
        StringBuilder sb = new StringBuilder();
        sb.append(str.charAt(0));
        sb.append(str.length()-2);
        sb.append(str.charAt(str.length()-1));
        return sb.toString();
    }

    public boolean isUnique(String word) {
        String key = generateKey(word);
        if(hashmap.containsKey(key)){
            HashSet<String> hashset = hashmap.get(key);
            return hashset.contains(word) && hashset.size() == 1;
        }
        return true;
    }
}

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