Solution: Word Ladder II
Explore the two-phase approach for solving the Word Ladder II problem by first using breadth-first search (BFS) to find the shortest paths between words and then applying depth-first search (DFS) backtracking to reconstruct all valid transformation sequences. Understand how to efficiently generate neighbors, track parents, and avoid revisiting words to produce all shortest word ladder sequences in a systematic way.
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Statement
You are given two words, beginWord and endWord, and a dictionary of words called wordList. Your task is to find all the shortest transformation sequences from beginWord to endWord, such that:
Only one letter can be changed at a time.
Each transformed word must exist in the given
wordList.The transformation sequence must begin with
beginWordand end withendWord.
Return all the shortest transformation sequences as a list of lists. If no valid transformation exists, return an empty list.
Constraints:
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