Shortest Transformation Sequence Length

Problem

Given a begin_word string, an end_word string, and a list of unique lowercase strings word_list, return the length of the shortest transformation sequence from begin_word to end_word. A valid transformation changes exactly one character at a time, and every intermediate word must exist in word_list. Return 0 if no such sequence exists.

Constraints

• 1 <= len(begin_word) <= 10
• len(begin_word) == len(end_word) == len(word_list[i])
• 1 <= len(word_list) <= 5000
• All strings contain only lowercase English letters
• All words in word_list are unique