DIY: Word Ladder I

Problem statement

You are given a list of words, a starting_word, and an ending_word. This problem requires you to find the minimum number of transitions required to convert the starting_word into the ending_wordunder the following constraints:

• All the words should be of the same length.

• There should be no duplicates in the given list.

• starting_word and ending_word should be non-empty.

• starting_word and ending_word should not be the same.

• A transition can only occur if two words differ by one character/alphabet.

• It should return an empty list if there is no such transformation sequence.

• All the words should contain only lowercase alphabetic characters.

Input

The following is an example input:

word_list = ["hot","dot","dog","lot","log","cog"]
start = "hit"
target = "cog"

Output

The following is an example output:

4

One shortest transformation can be "hit" -> "hot" -> "dot" -> "dog" -> "cog". It can be seen that it took 4 steps to reach the last word.

Coding exercise

For this coding exercise, you need to implement the word_ladder(starting_word, ending_word, word_list) function. The function will return the shortest transformation from the starting_word to the ending_word.