211 Add and Search Word - Data structure design

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.

click to show hint.

You should be familiar with how a Trie works. If not, please work on this problem: Implement Trie (Prefix Tree) first.

 

 

const int leafSize = 26;

class TrieNode
{
public:
    TrieNode():isLeaf(false)
    {
        fill_n(children,leafSize,nullptr);
    }
    
    bool isLeaf;
    TrieNode *children[leafSize];
};


class WordDictionary {
    TrieNode *root;
public:
    WordDictionary():root(new TrieNode)
    {
        
    }
    // Adds a word into the data structure.
    void addWord(string word) {
        TrieNode *index = root;
        TrieNode *temp = nullptr;
        std::size_t i = 0;
        for(;i < word.size();++i)
        {
            temp = index->children[word[i] - 'a'];
            if(nullptr == temp)
                index->children[word[i] - 'a'] = new TrieNode;
            index = index->children[word[i] - 'a'];
        }
        index->isLeaf = 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 search(word,root);
    }
    
    bool search(string word,TrieNode *p) {
        TrieNode *index = p;
        TrieNode *temp = nullptr;
        
        std::size_t i = 0;
        for(;i < word.size();++i)
        {
            if(word[i] == '.')
            {
                for(int j = 0;j < leafSize;++j)
                    if(index->children[j] && search(word.substr(i + 1),index->children[j]))
                        return true;
                return false;
            }
            else
            {
                temp = index->children[word[i] - 'a'];
                if(nullptr == temp)
                    return false;
                index = index->children[word[i] - 'a'];
            }
        }
        
        return index->isLeaf;
    }    
};

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