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Word Ladder II
Difficulty: Hard
Category: DSA
Topics: Array, String, Backtracking, Breadth-first Search
Asked at: Uber, Amazon, Facebook, Box, Lyft, Microsoft, Google, Bloomberg
A transformation sequence from word `beginWord` to word `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 "hot" -> "dot" -> "dog" -> "cog"
"hit" -> "hot" -> "lot" -> "log" -> "cog"
Example 2:
Input: beginWord = "hit", endWord = "cog", wordList = ["hot","dot","dog","lot","log"]
Output: []
Explanation: The endWord "cog" is not in wordList, therefore there is no valid transformation sequence.
Constraints:
`1 <= beginWord.length <= 10`
`endWord.length == beginWord.length`
`1 <= wordList.length <= 5000`
`wordList[i].length == beginWord.length`
`beginWord`, `endWord`, and `wordList[i]` consist of lowercase English letters.
`beginWord != endWord`
All the words in `wordList` are unique.
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