Word Ladder (Minimum Transformations)

Asked at Adobe · Coding Questions · Difficulty: Hard

Given two words (`beginWord` and `endWord`) and a dictionary word list, find the **minimum number of operations** needed to change `beginWord` into `endWord`. You may change only one letter at a time, and each intermediate word must exist in the word list. If there is no possible transformation, return `None` (Python) / `-1` (Java & C++) / `null` (JavaScript).

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