Word Ladder II

public class Solution {
    public List<List<String>> findLadders(String beginWord, String endWord, Set<String> wordList) {
        List<List<String>> res = new LinkedList<List<String>>();
        Map<String, Integer> visited = new HashMap<>();
        Queue<Node> queue = new LinkedList<>();
        List<Node> nodeList = new LinkedList<Node>();
        visited.put(beginWord, 0);
        queue.offer(new Node(beginWord));
        int lastCnt = 1;
        int currCnt = 0;
        int level = 1;
        boolean foundEndWord = false;

        while(!queue.isEmpty()) {
            Node currNode = queue.poll();
            StringBuilder wordBuff = new StringBuilder(currNode.word);
            lastCnt--;
            for(int i = 0; i < wordBuff.length(); i++) {
                char currChar = wordBuff.charAt(i);
                for(char c = 'a'; c <= 'z'; c++) {
                    if(c == currChar) {
                        continue;
                    }

                    wordBuff.setCharAt(i, c);
                    String tmpWord = wordBuff.toString();
                    Node tmpNode = new Node(tmpWord, currNode);

                    if(endWord.equals(tmpWord)) {
                        nodeList.add(tmpNode);
                        foundEndWord = true;
                    }

                    if(wordList.contains(tmpWord)) {
                        if(visited.containsKey(tmpWord) && visited.get(tmpWord)<level) {
                            continue;
                        }
                        currCnt++;
                        queue.offer(tmpNode);
                        visited.put(tmpWord, level);
                    }
                }
                wordBuff.setCharAt(i, currChar);
            }

            if(lastCnt == 0) {
                if(foundEndWord) {
                    break;
                }
                lastCnt = currCnt;
                currCnt = 0;
                level++;
            }
        }

        for(Node currNode: nodeList) {
            List<String> list = new LinkedList<>();
            list.add(currNode.word);
            while(currNode.parent != null) {
                list.add(0, currNode.parent.word);
                currNode = currNode.parent;
            }
            res.add(list);
        }

        return res;
    }

    class Node {
        Node parent;
        String word;

        public Node(String word){
            this.word = word;
        }

        public Node(String word, Node parent) {
            this.word = word;
            this.parent = parent;
        }
    }
}