[LintCode] Add and Search Word 添加和查找单词

Design a data structure that supports the following two operations: addWord(word) and 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.
Notice

You may assume that all words are consist of lowercase letters a-z.
Example

addWord("bad")
addWord("dad")
addWord("mad")
search("pad")  // return false
search("bad")  // return true
search(".ad")  // return true
search("b..")  // return true

LeetCode上的原题，请参见我之前的博客Add and Search Word - Data structure design。

class WordDictionary {
public:
    struct TrieNode {
        bool isLeaf;
        TrieNode *child[26];
    };

    WordDictionary() {
        root = new TrieNode();
    }

    // Adds a word into the data structure.
    void addWord(string word) {
        TrieNode *p = root;
        for (char c : word) {
            int i = c - ‘a‘;
            if (!p->child[i]) p->child[i] = new TrieNode();
            p = p->child[i];
        }
        p->isLeaf = 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) {
        search(word, root, 0);
    }

    bool search(string &word, TrieNode *p, int i) {
        if (i == word.size()) return p->isLeaf;
        if (word[i] == ‘.‘) {
            for (auto a : p->child) {
                if (a && search(word, a, i + 1)) return true;
            }
            return false;
        } else {
            return p->child[word[i] - ‘a‘] && search(word, p->child[word[i] - ‘a‘], i + 1);
        }
    }

private:
    TrieNode *root;
};