211. Add and Search Word - Data structure design

Posted 2020-08-22 鱼与海洋

Design a data structure that supports the following two operations:

void addWord(word)
bool search(word)

search(word) can search a literal word or a regular expression string containing only letters a-z or .. A .means it can represent any one letter.

For example:

addWord("bad")
addWord("dad")
addWord("mad")
search("pad") -> false
search("bad") -> true
search(".ad") -> true
search("b..") -> true

Note:
You may assume that all words are consist of lowercase letters a-z.

Use Tire

public class WordDictionary {
    class TrieNode {
        Map<Character, TrieNode> map;
        boolean isWord;
        public TrieNode(){
            map = new HashMap<>();
            isWord = false;
        }
    }
    private TrieNode root;
    public WordDictionary(){
        root = new TrieNode();
    }
    // Adds a word into the data structure.
    public void addWord(String word) {
        TrieNode node = root;
        for(char c : word.toCharArray()){
            if(!node.map.containsKey(c)){
                node.map.put(c, new TrieNode());
            }
            node =  node.map.get(c);
        }
        node.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 dfs(word.toCharArray() , 0 , root);
    }
    
    public boolean dfs(char[] words, int deep , TrieNode root){
        if(deep == words.length){
            return root.isWord;
        }
        if(words[deep] == ‘.‘){
            for(char s : root.map.keySet()){
                 if(dfs(words , deep+1 , root.map.get(s)))
                        return true;
            }
        }
        else{
            return root.map.containsKey(words[deep]) && dfs(words , deep+1 , root.map.get(words[deep]));
        } 
        return false;
    }
}

// Your WordDictionary object will be instantiated and called as such:
// WordDictionary wordDictionary = new WordDictionary();
// wordDictionary.addWord("word");
// wordDictionary.search("pattern");