Problem Word Ladder

Problem Description:

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

1. Only one letter can be changed at a time
2. Each intermediate word must exist in the dictionary

For 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:

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

Solution:

public int ladderLength(String start, String end, Set<String> dict) {
        if (dict.size() == 0) {
            return 0;
        }

        LinkedList<Integer> distanceQueue = new LinkedList<Integer>();
        LinkedList<String> wordQueue = new LinkedList<String>();

        wordQueue.add(start);
        distanceQueue.add(1);

        while (! wordQueue.isEmpty()){
            String currentword = wordQueue.pop();
            int currentDistance = distanceQueue.pop();

            if (currentword.equals(end)) {
                return currentDistance;
            }

for (int i = 0; i < currentword.length(); i++) {
                char ch = currentword.charAt(i);

                for (int c = 'a'; c <= 'z'; c++) {
                    if (ch != c) {
                        char[] charArray = currentword.toCharArray();
                        charArray[i] = (char)c;
                        String newWord = new String (charArray);

                        if (dict.contains(newWord)) {
                            wordQueue.add(newWord);
                            distanceQueue.add(currentDistance + 1);
                            dict.remove(newWord);
                        }
                    }
                }
            }
        }

        return 0;
    }