Add and Search Word

Trie 树的一个应用

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.

 

class TrieNode{
public:
    TrieNode* child[26];
    bool isWord = false;
    TrieNode() : isWord(false){
        for(auto &a : child)
            a = nullptr;
    }

};

class WordDictionary{
private:
    TrieNode* root = new TrieNode();
public:
    void addWord(string word){
        TrieNode* p = root;
        for(auto &a : word){
            int i = a - 'a';
            if(p->child[i] == nullptr) p->child[i] = new TrieNode();
            p = p->child[i];
        }
        p->isWord = true;
    }

    bool search(string word){
        int n = word.length();
        return search(word,n,0,root);
    }

    bool search(string& word,int n,int pos,TrieNode* cur){
        if(pos == n) return cur->isWord;
        if(cur == nullptr) return false;

        if(word[pos] == '.'){
            for(int i=0;i<26;i++){
                if(cur->child[i]){
                    if(search(word,n,pos+1,cur->child[i])){
                        return true;
                    }
                }
            }
        }else{
            int i = word[pos] - 'a';
            if(cur->child[i])
                return search(word,n,pos+1,cur->child[i]);
        }
        return false;
    }
};