211. 添加与搜索单词 - 数据结构设计题解

梦里梦外; 2021-12-13 13:33 161阅读 0赞

题解如下:

class WordDictionary {
    
        private class Node{
    
            public boolean isWord;
            public TreeMap<Character, Node> next;
    
            public Node(boolean isWord){
                this.isWord = isWord;
                next = new TreeMap<>();
            }
    
            public Node(){
                this(false);
            }
        }
    
        private Node root;
    
        /** Initialize your data structure here. */
        public WordDictionary() {
            root = new Node();
        }
    
        /** Adds a word into the data structure. */
        public void addWord(String word) {
            Node cur = root;
            for (int i = 0; i < word.length(); i++) {
                char c = word.charAt(i);
                if (cur.next.get(c) == null)
                    cur.next.put(c, new Node());
                cur = cur.next.get(c);
            }
            if (!cur.isWord)
                cur.isWord  = 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) {
            return match(root, word, 0);
        }
    
        private boolean match(Node node, String word, int index){
    
            if (index == word.length())
                return node.isWord;
    
            char c = word.charAt(index);
            if (c != '.'){
                if (node.next.get(c) == null)
                    return false;
                return match(node.next.get(c), word, index + 1);
            }
            else {
                for (char nextChar : node.next.keySet()) 
                    if (match(node.next.get(nextChar), word, index + 1))
                        return true;
                return false;
            }
        }
    }