Unique word abbreviation

Time: ctor:O(N),lookup:O(1); Space: O(K); easy

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 1:

Input: dictionary = {ValidWordAbbr} [“deer”, “door”, “cake”, “card”], word = “dear”

Output: False

Explanation:

  • Dictionary’s abbreviation is [“d2r”, “d2r”, “c2e”, “c2d”].

  • “dear” ’s abbreviation is “d2r” , in dictionary.

Example 2:

Input: dictionary = {ValidWordAbbr} [“deer”, “door”, “cake”, “card”], word = “card”

Output: True

Explanation:

  • Dictionary’s abbreviation is [“d2r”, “d2r”, “c2e”, “c2d”].

  • “cart” ’s abbreviation is “c2t” , not in dictionary.

Example 3:

Input: dictionary = {ValidWordAbbr} [“deer”, “door”, “cake”, “card”], word = “cane”

Output: False

Explanation:

  • Dictionary’s abbreviation is [“d2r”, “d2r”, “c2e”, “c2d”].

  • “cane” ’s abbreviation is “c2e” , in dictionary.

Example 4:

Input: dictionary = {ValidWordAbbr} [“deer”, “door”, “cake”, “card”], word = “make”

Output: True

Explanation:

  • Dictionary’s abbreviation is [“d2r”, “d2r”, “c2e”, “c2d”].

  • “make” ’s abbreviation is “m2e” , not in dictionary.

[1]:

import collections

class ValidWordAbbr(object):
    def __init__(self, dictionary):
        """
        initialize your data structure here.
        :type dictionary: List[str]
        """
        self.lookup_ = collections.defaultdict(set)

        for word in dictionary:
            abbr = self.abbreviation(word)
            self.lookup_[abbr].add(word)

    def isUnique(self, word):
        """
        check if a word is unique.
        :type word: str
        :rtype: bool
        """
        abbr = self.abbreviation(word)
        return self.lookup_[abbr] <= {word}

    def abbreviation(self, word):
        if len(word) <= 2:
            return word
        return word[0] + str(len(word)-2) + word[-1]

[2]:

dictionary = ["deer", "door", "cake", "card"]
s = ValidWordAbbr(dictionary)

word = "dear"
assert s.isUnique( word) == False

word = "card"
assert s.isUnique( word) == True

word = "cane"
assert s.isUnique( word) == False

word = "make"
assert s.isUnique( word) == True