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 :

Given:

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.

Note:

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