Problem Brief
Determine the Edit Distance in a Word Ladder
OA
Given two words (beginWord and endWord), and a dictionary's word list, find the minimum number of operations needed to change beginWord into endWord.
You can 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).
1Example 1
Input
beginWord = "hit", endWord = "cog", wordList = ["hit", "hot", "dot", "dog", "cog"]
Output
4
Explanation
The transformation sequence can be: hit -> hot -> dot -> dog -> cog, which is 4 steps long.
2Example 2
Input
beginWord = "word", endWord = "word", wordList = ["word", "ward"]
Output
0
Explanation
Since the beginWord is the same as the endWord, no transformation is needed, so the number of steps is 0.
3Example 3
Input
beginWord = "hit", endWord = "cog", wordList = ["hit", "hot", "dot", "dog"]
Output
-1
Explanation
The word cog is not in the list, so there is no possible transformation sequence.