lintcode-medium-Add and Search Word

Design a data structure that supports the following two operations: addWord(word) and 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.

addWord("bad")
addWord("dad")
addWord("mad")
search("pad")  // return false
search("bad")  // return true
search(".ad")  // return true
search("b..")  // return true

这题细说太麻烦，看看trie/prefix tree就解决了

public class WordDictionary {
    
    class TrieNode{
        char c;
        HashMap<Character, TrieNode> children;
        boolean isLeaf;
        
        public TrieNode(){
            this.children = new HashMap<Character, TrieNode>();
            this.isLeaf = false;
        }
        
        public TrieNode(char c){
            this.c = c;
            this.children = new HashMap<Character, TrieNode>();
            this.isLeaf = false;
        }
    }
    
    TrieNode root;
    
    public WordDictionary(){
        this.root = new TrieNode();
    }
    

    // Adds a word into the data structure.
    public void addWord(String word) {
        // Write your code here
        
        if(word == null || word.length() == 0)
            return;
        
        TrieNode temp = root;
        
        for(int i = 0; i < word.length(); i++){
            char c = word.charAt(i);
            
            if(temp.children.containsKey(c)){
                temp = temp.children.get(c);
            }
            else{
                temp.children.put(c, new TrieNode(c));
                temp = temp.children.get(c);
            }
            
            if(i == word.length() - 1)
                temp.isLeaf = true;
        }
        
        return;
    }

    // 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) {
        // Write your code here
        
        if(word == null || word.length() == 0)
            return true;
        
        char[] array = word.toCharArray();
        
        return search(root, array, 0);
    }
    
    public boolean search(TrieNode root, char[] array, int start){
        if(start == array.length && root.isLeaf)
            return true;
        else if(start == array.length)
            return false;
        
        if(array[start] != '.'){
            if(root.children.containsKey(array[start]))
                return search(root.children.get(array[start]), array, start + 1);
            else
                return false;
        }
        else{
            for(Map.Entry<Character, TrieNode> entry: root.children.entrySet()){
                if(search(root.children.get(entry.getKey()), array, start + 1))
                    return true;
            }
            return false;
        }
    }
    
}

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