Determine Whether a Word Transformation Exists
Company: Snapchat
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: medium
Interview Round: Technical Screen
Given a `beginWord`, an `endWord`, and a list of valid words `wordList`, determine whether it is possible to transform `beginWord` into `endWord`.
Rules:
- Each transformation changes exactly one character.
- Every transformed word must exist in `wordList`.
- All words contain only lowercase English letters and have the same length.
- Return `true` if at least one valid transformation sequence exists; otherwise return `false`.
Example:
- Input: `beginWord = "hit"`, `endWord = "cog"`, `wordList = ["hot", "dot", "dog", "lot", "log", "cog"]`
- Output: `true`
Because one valid sequence is:
`hit -> hot -> dot -> dog -> cog`
You only need to return a boolean value, not the length of the shortest transformation.
Quick Answer: This question evaluates a candidate's ability to model single-character word transformations as a graph/search problem, testing competencies in graph traversal, string manipulation, and state-space connectivity within the Coding & Algorithms domain.
Return whether beginWord can reach endWord by changing one character at a time through wordList words.
Constraints
- Inputs are Python literals matching the function signature.
- Return a deterministic exact-match value.
Examples
Input: ('hit','cog',['hot','dot','dog','lot','log','cog'])
Expected Output: True
Explanation: A valid ladder exists.
Input: ('hit','cog',['hot','dot','dog','lot','log'])
Expected Output: False
Explanation: The end word is unavailable.
Input: ('a','c',['a','b','c'])
Expected Output: True
Explanation: Single-character transformations are supported.
Hints
- Bucket words by wildcard patterns.
- Run BFS from beginWord until endWord is found.