LeetCode-211 添加与搜索单词

class WordDictionary {
    //使用什么来存储单词 ------>字典树？？

    //字典树
    // 1 新建节点
    static class TireNode{
        boolean flag ; //记录该单词是否出现
        Map<Character, TireNode> childNode;
        
        public TireNode()
        {
            flag = false;
            childNode = new HashMap<Character, TireNode>();
        }
    }
    TireNode node;
   
    /** Initialize your data structure here. */
    public WordDictionary() {
        node = new TireNode(); //新建根节点,不存储任何字符
    }
    
    /** Adds a word into the data structure. */
    //添加一个单词
    public void addWord(String word) {
        char[] letter = word.toCharArray();
          TireNode curnode = node;
        for(int i = 0 ; i < letter.length ; i++)
        {
            char cur = letter[i];
            //从根节点寻找
            if(!curnode.childNode.containsKey(cur)) //子节点不存在就添加
            {
                curnode.childNode.put(cur,new TireNode());
            }
            curnode = curnode.childNode.get(cur);
        }
        curnode.flag = true;
        
    }
    
    /** Returns if the word is in the data structure. A word could contain the dot character '.' to represent any one letter. */
    public boolean search(String word) {
       TireNode root = node;
        return backstack(root,word,0);
    
      
}

    private boolean backstack(TireNode root , String str, int index)
    {
         if(index == str.length())return root.flag;
         char i = str.charAt(index);
         if(i == '.')
         {
                //遍历当前节点下的所有子节点
                for(Map.Entry<Character, TireNode> entry : root.childNode.entrySet()){
                    if(entry.getKey() != null && backstack(entry.getValue(),str,index+1))
                    {
                        //存在一个就返回true
                        return true;
                    }
                }
                return false;
         }
         else
         {
            if(!root.childNode.containsKey(i))
            {
                  return false;
            }
            //直接进入下一个节点
            return backstack(root.childNode.get(i),str , index+1);
           
         }


    }
}