My code:

public class Solution {
    private class wordNode {
        String word;
        int step;
        wordNode(String word, int step) {
            this.word = word;
            this.step = step;
        }
    }
    
    public int ladderLength(String beginWord, String endWord, Set<String> wordList) {
        Queue<wordNode> q = new LinkedList<wordNode>();
        q.offer(new wordNode(beginWord, 1));
        wordList.add(endWord);
        while (!q.isEmpty()) {
            wordNode node = q.poll();
            if (node.word.equals(endWord)) {
                return node.step;
            }
            char[] arr = node.word.toCharArray();
            for (int i = 0; i < arr.length; i++) {
                for (char c = 'a'; c <= 'z'; c++) {
                    char temp = arr[i];
                    arr[i] = c;
                    String newWord = String.valueOf(arr);
                    if (wordList.contains(newWord)) {
                        q.offer(new wordNode(newWord, node.step + 1));
                        wordList.remove(newWord);
                    }
                    arr[i] = temp;
                }
            }
        }
        return 0;
    }
}

reference:
http://www.programcreek.com/2012/12/leetcode-word-ladder/

拖了太久一直没做这两道题目。今天全给做了。
这道题目就是BFS，然后我一直在想，怎么把一个单词变成list上的单词。结果方法很纯粹，暴力搜索。

Anyway, Good luck, Richardo! — 09/27/2016