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

// Solution 1. Hash Table, 62ms, 100%.
class WordDictionary {
public:
    WordDictionary() {}
    
    void addWord(string word) {
        words[word.size()].push_back(word);
    }
    
    bool search(string word) {
        for(auto s: words[word.size()]) if(isEqual(s, word)) return true;
        return false;
    }
    
private:
    unordered_map<int, vector<string>>words;
    
    bool isEqual(string a, string b){
        for(int i = 0; i < a.size(); i++){
            if(b[i] == '.') continue;
            if(a[i] != b[i]) return false;
        }
        return true;
    }
};

// Solution 2. Trie, 88ms.
struct TrieNode{
    bool isKey;
    TrieNode* next[26];
    TrieNode():isKey(false){
        memset(next, NULL, sizeof(next));
    }
};

class WordDictionary {
public:
    WordDictionary() {
        root = new TrieNode();
    }
    
    void addWord(string word) {
        TrieNode* node = root;
        for(auto c: word){
            if(!node->next[c - 'a']) node->next[c - 'a'] = new TrieNode();
            node = node->next[c - 'a'];
        }
        node->isKey = true;
    }
    
    bool search(string word) {
        return helper(word, root);
    }

private:
    TrieNode* root;
    
    bool helper(string word, TrieNode* node){
        for(int i = 0; i < word.size(); i++){
            char c = word[i];
            if(c != '.'){
                if(!node->next[c - 'a']) return false;
                node = node->next[c - 'a'];
            }
            else{
                bool found = false;
                int j = 0;
                for(; j < 26; j++){
                    if(node->next[j]) found |= helper(word.substr(i + 1), node->next[j]);
                    if(found) return true;
                }
                if(j == 26) return false;
            }
        }
        return node->isKey;
    }
};