#leetcode wordladder

WordLadder.java

import java.util.Queue;
import java.util.LinkedList;
import java.util.Hashtable;
import java.util.Arrays;
public class Solution {
    	public int ladderLength(String start, String end, Set<String> dict) {
		if (start.equals(end))
			return 1;

		// add the string end to the dict
		dict.add(end);
		Queue<String> q = new LinkedList<String>();
		q.offer(start);

		Hashtable<String, Integer> lengths = new Hashtable<String, Integer>();
		lengths.put(start, 1);

		while (q.size() > 0) {
			String current = q.poll();
			if (current.equals(end))
				break;
			int tmpLen = lengths.get(current);

			// discover the edges
			// we need to change every single character in the current string
			// for 26 times
			// and to see if the new word is in the dict and not in the lengths
			// table
			for (int i = 0; i < current.length(); i++) {
				char[] word = current.toCharArray();
				char ch = word[i];
				for (char c = 'a'; c <= 'z'; c++) {
					word[i] = c;
					String newWord = new String(word);
					if (dict.contains(newWord) && !lengths.containsKey(newWord)) {
						lengths.put(newWord, tmpLen + 1);
						q.offer(newWord);
					}
				}
				word[i] = ch; // remember to change it back before we move on to
								// the next position
			}
		}
		if (lengths.containsKey(end))
			return lengths.get(end);
		return 0;
	}
}