Word Ladder

Solution.java

package WordLadder;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

class Solution {
    public int ladderLength(String beginWord, String endWord, List<String> wordList) {
        HashSet<String> c = new HashSet<>();
        c.addAll(wordList);

        int result = 0;
        boolean found = false;
        Set<String> visited = new HashSet<>();
        List<String> queue = new ArrayList<>();
        queue.add(beginWord);
        visited.add(beginWord);

        while (!found && !queue.isEmpty()) {
            result++;
            List<String> nextQueue = new ArrayList<>();

            for (String s : queue) {
                if (endWord.equals(s)) {
                    found = true;
                    break;
                }
                for (int i = 0; i < s.length(); i++) {
                    char[] chars = s.toCharArray();
                    for (char o = 'a'; o <= 'z'; o++) {
                        chars[i] = o;
                        String ns = new String(chars);
                        if (visited.contains(ns)) continue;
                        if (!c.contains(ns)) continue;
                        visited.add(ns);
                        nextQueue.add(ns);
                    }
                }
            }

            queue = nextQueue;
        }
        return found ? result : 0;
    }
}