LeetCode 676. 实现一个魔法字典

思路

首先创建字典树，之后对字典树进行dfs搜索。

代码实现

class Trie {
public:
    bool isWord;
    Trie* next[26];

    void insert(const string word) {
        Trie* t = this;
        for(int i = 0; i < word.length(); ++i) {
            if(t->next[word[i]-'a'] == NULL)
                t->next[word[i]-'a'] = new Trie();
            t = t->next[word[i]-'a'];
        }

        t->isWord = true;
    }
};


class MagicDictionary {
private:
    Trie* t;
public:
    /** Initialize your data structure here. */
    MagicDictionary() {
        t = new Trie();
    }
    
    void buildDict(vector<string> dictionary) {
        for(const string &word: dictionary) {
            t->insert(word);
        }
    }
    
    bool search(string searchWord) {
        return dfs(t, searchWord, 0, false);
    }

    //isMod为true时，表示已经替换了一个字母
    bool dfs(Trie* t, const string& word, int index, bool isMod) {
        if(t == NULL)
            return false;
        if(index > word.length())
            return false;
        if(index == word.length() ) 
            return t->isWord && isMod;
        
        for(int i = 0; i < 26; ++i) {
            if(t->next[i] != NULL) {
                if(i == word[index]-'a') {
                    //注意这里不能直接 return dfs(t->next[i], word, index+1, isMod);
                    //这样直接return dfs会导致无法搜索到后续的for循环的情况
                    if(dfs(t->next[i], word, index+1, isMod))
                        return true;
                }else {
                    if(!isMod && dfs(t->next[i], word, index+1, true))
                        return true;
                }
            }
        }

        return false;
    }
};

/**
 * Your MagicDictionary object will be instantiated and called as such:
 * MagicDictionary* obj = new MagicDictionary();
 * obj->buildDict(dictionary);
 * bool param_2 = obj->search(searchWord);
 */

 

参考

LeetCode 实现一个魔法字典（前缀树）