Word Ladder (#127)

A transformation sequence from word beginWord to 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.
• sk == endWord.

Given two words, beginWord and endWord, and a dictionary wordList, return the length of the shortest transformation sequence from beginWord to endWord, or 0 if no such sequence exists.

Company Tags: Google, Amazon

Core Concept: Graph, BFS

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