Word Ladder

Hard

Graph · BFS · String~30m

00:00

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Section 01

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Problem statement

A transformation sequence from word `beginWord` to word `endWord` using a dictionary `wordList` is a sequence of words `beginWord -> s₁ -> s₂ -> ... -> sₖ` such that every adjacent pair of words differs by a single letter, every `sᵢ` for `1 ≤ i ≤ k` is in `wordList` (note that `beginWord` does not need to be in `wordList`), and `sₖ == endWord`. Given two words, `beginWord` and `endWord`, and a dictionary `wordList`, return the number of words in the shortest transformation sequence from `beginWord` to `endWord`, or `0` if no such sequence exists.

Example

begin = "hit", end = "cog", wordList = ["hot","dot","dog","lot","log","cog"] → 5

Constraints

1 ≤ beginWord.length ≤ 10 · endWord.length == beginWord.length · 1 ≤ wordList.length ≤ 5000 · wordList[i].length == beginWord.length · all words consist of lowercase English letters

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