[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;
};