Word Ladder I

Given two words (start and end), and a dictionary, find the length of shortest transformation sequence from start to end, such that:

  • You must change exactly one character in every transformation
  • Each intermediate word must exist in the dictionary

Example :


start = "hit"
end = "cog"
dict = ["hot","dot","dog","lot","log"]

As one shortest transformation is "hit" -> "hot" -> "dot" -> "dog" -> "cog",
return its length 5.

Note that we account for the length of the transformation path instead of the number of transformation itself.


  • Return 0 if there is no such transformation sequence.
  • All words have the same length.
  • All words contain only lowercase alphabetic characters.
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