Vowel Spellchecker Python Solution with Tests

LeetCode 966, Medium. Topics: Array, Hash Table, String. View on LeetCode. Generate this problem as a practice environment: tested reference solution, 18 parametrized pytest cases, and a playground notebook:

lcpy gen -n 966   # by problem number
lcpy gen -s vowel_spellchecker   # by problem name

Problem

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.
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.

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 capitalization, 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].

Examples

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"]

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 English letters.

Solution

Reference implementation from solution.py on GitHub, full suite in test_solution.py:

class Solution:
    # Time: O((W + Q) * L) where W = len(wordlist), Q = len(queries), L = max word length
    # Space: O(W * L)
    def spellchecker(self, wordlist: list[str], queries: list[str]) -> list[str]:
        vowels = set("aeiou")

        def mask(word: str) -> str:
            return "".join("*" if c in vowels else c for c in word.lower())

        words = set(wordlist)
        case_insensitive: dict[str, str] = {}
        vowel_insensitive: dict[str, str] = {}
        for word in wordlist:
            case_insensitive.setdefault(word.lower(), word)
            vowel_insensitive.setdefault(mask(word), word)

        answer: list[str] = []
        for query in queries:
            if query in words:
                answer.append(query)
            elif query.lower() in case_insensitive:
                answer.append(case_insensitive[query.lower()])
            elif mask(query) in vowel_insensitive:
                answer.append(vowel_insensitive[mask(query)])
            else:
                answer.append("")
        return answer

Complexity

Time	Space
O((W + Q) * L) where W = len(wordlist), Q = len(queries), L = max word length	O(W * L)

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Vowel Spellchecker Python Solution with Tests

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