211. Add and Search Word - Data structure design ----M

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.

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.

A:
思路很直接，就是 用 Trie 解决。  (这里，仍然需要自己定义TrieNode)

*********** Solution 1： Trie *******************

class WordDictionary {
public:
    /** Initialize your data structure here. */
    WordDictionary() {
        root = new TrieNode('2',true);
    }
    
    /** Adds a word into the data structure. */
    void addWord(string word) {
        auto runner = root;
        for(int i =0;i<word.length();i++){
            char ch = word[i];
            if(runner->map.find(ch) == runner->map.end()){
                TrieNode * tmp = new TrieNode(ch, i == word.length()-1);
                runner->map[ch] = tmp;
            }
            runner = runner->map[ch];
        }
        runner->isEnd = true;
    }
    
    /** Returns if the word is in the data structure. A word could contain the dot character '.' to represent any one letter. */
    bool search(string word) {
        return searchHelper(word, root);
    }
private:
    struct TrieNode{
        char ch;
        bool isEnd;
        unordered_map<char, TrieNode*> map;
        TrieNode(char curChar, bool end){
            ch = curChar;
            isEnd = end;
        }
    };
    bool searchHelper(string word, const TrieNode* node){        
        if(word.length() ==0)
            return node->isEnd;
        auto runner = root;
        char ch = word[0];
        if(ch == '.'){
            auto iter = node->map.begin();
            while(iter != node->map.end()){
                int subResult = searchHelper(word.substr(1), iter->second );
                if(subResult)
                    return true;
                iter++;
            }
        }
        if(node->map.find(ch) == node->map.end()){
            return false;
        }else{
            return searchHelper(word.substr(1), node->map.find(ch)->second);
        }
    }

    TrieNode *root;
};

/**
 * Your WordDictionary object will be instantiated and called as such:
 * WordDictionary* obj = new WordDictionary();
 * obj->addWord(word);
 * bool param_2 = obj->search(word);
 */

Mistakes:


第二次  Trie Node 用的array，而非HashMap

public class WordDictionary {
    TrieNode root = new TrieNode();
    // Adds a word into the data structure.
    public void addWord(String word) {
        aHelper(word,root);
    }
    private void aHelper(String word, TrieNode root){
        if(word.length()==0){
            root.isLeaf = true;
            return;
        }
        char ch = word.charAt(0);
        if(root.child[ch-'a'] ==null)
            root.child[ch-'a'] = new TrieNode();
        aHelper(word.substring(1),root.child[ch-'a']);
    }
    // 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 sHelper(root,word);
    }
    private boolean sHelper(TrieNode root, String word){
        if(root == null)
            return false;
        if(word.length()==0)
            return root.isLeaf;
        char ch = word.charAt(0);
        word = word.substring(1);
        if(ch != '.'){
            return sHelper(root.child[ch-'a'], word);
        }else{
            for(int i =0;i< 26;i++){
                if( sHelper(root.child[i], word))
                    return true;
            }
            return false;
        }
    }
}
class TrieNode{
    public boolean isLeaf;
    TrieNode child[] ;
    public TrieNode(){
        child = new TrieNode[26];
        isLeaf = false;
    }
}
// Your WordDictionary object will be instantiated and called as such:
// WordDictionary wordDictionary = new WordDictionary();
// wordDictionary.addWord("word");
// wordDictionary.search("pattern");