单词接龙问题

Posted 2022-02-13 Alice_yufeng

class Solution 
    Map<String, Integer> wordId = new HashMap<String, Integer>();
    List<List<Integer>> edge = new ArrayList<List<Integer>>();
    int nodeNum = 0;

    public int ladderLength(String beginWord, String endWord, List<String> wordList) 
        for (String word : wordList) 
            addEdge(word);
        
        addEdge(beginWord);
        if (!wordId.containsKey(endWord)) 
            return 0;
        
        int[] dis = new int[nodeNum];
        Arrays.fill(dis, Integer.MAX_VALUE);
        int beginId = wordId.get(beginWord), endId = wordId.get(endWord);
        dis[beginId] = 0;

        Queue<Integer> que = new LinkedList<Integer>();
        que.offer(beginId);
        while (!que.isEmpty()) 
            int x = que.poll();
            if (x == endId) 
                return dis[endId] / 2 + 1;
            
            for (int it : edge.get(x)) 
                if (dis[it] == Integer.MAX_VALUE) 
                    dis[it] = dis[x] + 1;
                    que.offer(it);
                
            
        
        return 0;
    

    public void addEdge(String word) 
        addWord(word);
        int id1 = wordId.get(word);
        char[] array = word.toCharArray();
        int length = array.length;
        for (int i = 0; i < length; ++i) 
            char tmp = array[i];
            array[i] = '*';
            String newWord = new String(array);
            addWord(newWord);
            int id2 = wordId.get(newWord);
            edge.get(id1).add(id2);
            edge.get(id2).add(id1);
            array[i] = tmp;
        
    

    public void addWord(String word) 
        if (!wordId.containsKey(word)) 
            wordId.put(word, nodeNum++);
            edge.add(new ArrayList<Integer>());