211 Add and Search Word - Data structure design 添加与搜索单词

设计一个支持以下两个操作的数据结构：
void addWord(word)
bool search(word)
search(word) 可以搜索文字或正则表达式字符串，字符串只包含字母 . 或 a-z 。 . 意味着它可以代表任何一个字母。
例如：
addWord("bad")
addWord("dad")
addWord("mad")
search("pad") -> false
search("bad") -> true
search(".ad") -> true
search("b..") -> true
注意事项:
你可以假设所有单词都是由小写字母 a-z 组成的。

详见：https://leetcode.com/problems/add-and-search-word-data-structure-design/description/

Java实现：

class TrieNode {

    public TrieNode[] children;

    public boolean isWord = false;

    public TrieNode(){

        children=new TrieNode[26];

    }

}

class WordDictionary {

    private TrieNode root;

    /** Initialize your data structure here. */

    public WordDictionary() {

        root=new TrieNode();

    }

    /** Adds a word into the data structure. */

    public void addWord(String word) {

        TrieNode node = root;

        for (char ch: word.toCharArray()) {

            if (node.children[ch-'a'] == null) {

                node.children[ch-'a'] = new TrieNode();

            }

            node = node.children[ch-'a'];

        }

        node.isWord = true;

    }

    /** Returns if the word is in the data structure. A word could contain the dot character '.' to represent any one letter. */

    public boolean search(String word) {

        return helper(word, 0, root);

    }

    private boolean helper(String word, int start, TrieNode node) {

        if (start == word.length()){

            return node.isWord;

        }

        char ch = word.charAt(start);

        if (ch == '.') {

            for (int i = 0; i < 26; i++) {

                if (node.children[i] != null && helper(word, start+1, node.children[i])) {

                    return true;

                }

            }

        } else {

            return node.children[ch-'a'] != null && helper(word, start+1, node.children[ch-'a']);

        }

        return false;

    }

}

/**

 * Your WordDictionary object will be instantiated and called as such:

 * WordDictionary obj = new WordDictionary();

 * obj.addWord(word);

 * boolean param_2 = obj.search(word);

 */

C++实现：

class TrieNode {

public:

    TrieNode *next[26];

    char c;

    bool isWord;

    TrieNode() : isWord(false) {

        for (auto & c: next)

        {

            c=nullptr;

        }

    }

    TrieNode(char _c):c(_c),isWord(false)

    {

        for(auto &c:next)

        {

            c=nullptr;

        }

    }

};

class WordDictionary {

public:

    WordDictionary() {

        root = new TrieNode();

    }

    // Adds a word into the data structure.

    void addWord(string word) {

        TrieNode *p = root;

        for (auto &c : word)

        {

            int i = c - 'a';

            if (!p->next[i])

            {

                p->next[i] = new TrieNode(c);

            }

            p = p->next[i];

        }

        p->isWord = 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 searchWord(word, root, 0);

    }

    bool searchWord(string &word, TrieNode *p, int i) {

        if (i == word.size())

        {

            return p->isWord;

        }

        if (word[i] == '.')

        {

            for (auto &c : p->next)

            {

                if (c && searchWord(word, c, i + 1))

                {

                    return true;

                }

            }

            return false;

        }

        else

        {

            return p->next[word[i] - 'a'] && searchWord(word, p->next[word[i] - 'a'], i + 1);

        }

    }

private:

    TrieNode *root;

};

// Your WordDictionary object will be instantiated and called as such:

// WordDictionary wordDictionary;

// wordDictionary.addWord("word");

// wordDictionary.search("pattern");

参考：https://www.cnblogs.com/grandyang/p/4507286.html

巴特西

211 Add and Search Word - Data structure design 添加与搜索单词 - 数据结构设计

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