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Vowel Spellchecker

Problem Statement​

Given a wordlist, we want to implement a spellchecker that converts a query word into a correct word.

For a given query word, the spell checker handles two categories of spelling mistakes:

Capitalization: If the query matches a word in the wordlist (case-insensitive), then the query word is returned with the same case as the case in the wordlist.

  • Example: wordlist = ["yellow"], query = "YellOw": correct = "yellow"
  • Example: wordlist = ["Yellow"], query = "yellow": correct = "Yellow"
  • Example: wordlist = ["yellow"], query = "yellow": correct = "yellow"

Vowel Errors: If after replacing the vowels ('a', 'e', 'i', 'o', 'u') of the query word with any vowel individually, it matches a word in the wordlist (case-insensitive), then the query word is returned with the same case as the match in the wordlist.

  • Example: wordlist = ["YellOw"], query = "yollow": correct = "YellOw"
  • Example: wordlist = ["YellOw"], query = "yeellow": correct = "" (no match)
  • Example: wordlist = ["YellOw"], query = "yllw": correct = "" (no match)

In addition, the spell checker operates under the following precedence rules:

  • When the query exactly matches a word in the wordlist (case-sensitive), you should return the same word back.
  • When the query matches a word up to capitlization, you should return the first such match in the wordlist.
  • When the query matches a word up to vowel errors, you should return the first such match in the wordlist.

If the query has no matches in the wordlist, you should return the empty string. Given some queries, return a list of words answer, where answer[i] is the correct word for query = queries[i].

Leetcode Link

Example 1:​

Input: wordlist = ["KiTe","kite","hare","Hare"], queries = ["kite","Kite","KiTe","Hare","HARE","Hear","hear","keti","keet","keto"]
Output: ["kite","KiTe","KiTe","Hare","hare","","","KiTe","","KiTe"]

Example 2:​

Input: wordlist = ["yellow"], queries = ["YellOw"]
Output: ["yellow"]

Constraints:​

  • 1 <= wordlist.length, queries.length <= 5000
  • 1 <= wordlist[i].length, queries[i].length <= 7
  • wordlist[i] and queries[i] consist only of only English letters.

Code​

Python Code

class Solution:
    def spellchecker(self, wordlist: List[str], queries: List[str]) -> List[str]:

        f = lambda x: ''.join('$' if ch in 'aeiou' else ch for ch in x)
        cap, vow = defaultdict(str), defaultdict(str)
        word_set, ans = set(wordlist), []

        for w in wordlist:                      # Build the dicts

            wLow = w.lower()
            if not cap[wLow]: cap[wLow] = w     # <–– Case 1: capital-check

            wVow = f(wLow)
            if not vow[wVow]: vow[wVow] = w     # <–– Case 2: vowel-check

        for q in queries:
            qLow, qVow, res = q.lower(), f(q.lower()), ''

            if q in word_set: res = q           # <–– word is in wordlist
            elif qLow in cap: res = cap[qLow]   # <–– cap-checked word is in wordlist
            elif qVow in vow: res = vow[qVow]   # <–– vowel-checked word is in wordlist

            ans.append(res)