Shortest Word Distance II — LeetCode 244 Python Solution

The problem

Design a data structure that will be initialized with a string array, and then it should answer queries of the shortest distance between two different strings from the array. Implement the WordDistance class: WordDistance(String[] wordsDict) initializes the object with the strings array wordsDict.

Example

Input

["WordDistance", "shortest", "shortest"]

Output

[null, 3, 1]

Explanation

WordDistance wordDistance = new WordDistance(["practice", "makes", "perfect", "coding", "makes"]);

Python solution

class WordDistance:
    def __init__(self, wordsDict: List[str]):
        self.d = defaultdict(list)
        for i, w in enumerate(wordsDict):
            self.d[w].append(i)

    def shortest(self, word1: str, word2: str) -> int:
        a, b = self.d[word1], self.d[word2]
        ans = inf
        i = j = 0
        while i < len(a) and j < len(b):
            ans = min(ans, abs(a[i] - b[j]))
            if a[i] <= b[j]:
                i += 1
            else:
                j += 1
        return ans


# Your WordDistance object will be instantiated and called as such:
# obj = WordDistance(wordsDict)
# param_1 = obj.shortest(word1,word2)

Complexity

Pattern: Two Pointers

Use the order already in the input to discard half the search space at every step. LeetCode 244. Shortest Word Distance II is filed here because LeetCode tags it Two Pointers, which is the vocabulary this hub collects.

The two pointers guide has the Python template for the pattern and the 201 LeetCode problems that use it.

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