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Implement Magic Dictionary

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Description

https://leetcode.com/problems/implement-magic-dictionary/description/

Solution

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class TrieNode {
public:
    unordered_map<char, TrieNode*> mapping;
    bool endFlag;
    TrieNode() {
        endFlag = false;
    }
};

class MagicDictionary {
private:
  TrieNode* root;  
public:
    /** Initialize your data structure here. */
    MagicDictionary() {
        root = new TrieNode();
    }
    
    /** Build a dictionary through a list of words */
    void buildDict(vector<string> dict) {
        for (auto& item: dict) {
            TrieNode* traverse = root;
            for (int i = 0; i < item.size(); ++i) {
                auto iter = traverse->mapping.find(item[i]);
                if (iter == traverse->mapping.end()) traverse->mapping[item[i]] = new TrieNode();
                traverse = traverse->mapping[item[i]];
            }
            traverse->endFlag = true;
        }
        
        return;
    }
    
    /** Returns if there is any word in the trie that equals to the given word after modifying exactly one character */
    bool search(string word) {
        bool success = false;
        helper(false, root, 0, word, success);
        return success;
    }
    
    void helper(bool tag, TrieNode* cur, int index, string& word, bool& success) {
        if (index == word.size()) {
            if (tag == true && cur->endFlag == true) success = true;
            return;
        }
            
        for (auto& item : cur->mapping) {
            if (item.first != word[index] && tag == false) {
                helper(true, item.second, index + 1, word, success);
            }
            if (item.first == word[index]) {
                helper(tag, item.second, index + 1, word, success);
            }
        }
        
        return;
    }
};

/**
 * Your MagicDictionary object will be instantiated and called as such:
 * MagicDictionary obj = new MagicDictionary();
 * obj.buildDict(dict);
 * bool param_2 = obj.search(word);
 */