Add and Search Word - Data structure design -- leetcode

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.

基本思路：

Implement Trie (Prefix Tree)

和上面问题差不多。需要实现一个字典树。

不同的是，支持‘.‘这个符号的查找时，需要用到递归。进行多路径偿试。

class WordDictionary {
public:

    WordDictionary() : root(new TrieNode()) {}

    // Adds a word into the data structure.
    void addWord(string word) {
        TrieNode *runner = root;
        for (auto ch: word) {
            runner = runner->get(ch, true);
        }
        runner->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 search(word, 0, root);
    }

private:
    class TrieNode {
    public:
        TrieNode() : branch(26), isword(false) {}

        TrieNode *get(char ch, bool create = false) {
            const int index = ch - 'a';
            if (!branch[index] && create)
                branch[index] = new TrieNode();
            return branch[index];
        }

        vector<TrieNode*> branch;
        bool isword;
    };

    bool search(const string &word, int index, TrieNode *node) {
        if (!node)
            return false;
        if (index == word.size())
            return node->isword;
        if (word[index] != '.')
            return search(word, index+1, node->get(word[index]));

        for (char ch='a'; ch<='z'; ch++) {
            if (search(word, index+1, node->get(ch)))
                return true;
        }
        return false;
    }

    TrieNode *root;
};

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

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