Lintcode 单词的添加与查找

 单词的添加与查找

 描述
 笔记

 数据

 评测

设计一个包含下面两个操作的数据结构：

addWord(word)

, 

search(word)

addWord(word)

会在数据结构中添加一个单词。而

search(word)

则支持普通的单词查询或是只包含

.

和

a-z

的简易正则表达式的查询。
一个 

.

 可以代表一个任何的字母。

您在真实的面试中是否遇到过这个题？ 

Yes


 注意事项

你可以假设所有的单词都只包含小写字母 a-z。

样例

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

AC代码如下：

struct trieNode {
trieNode() : terminableSize(0) {
for (int i = 0; i < 26; ++i) {
children[i] = NULL;
}
}

~trieNode() {
for (int i = 0; i < 26; ++i) {
if (children[i]) {
delete children[i];
children[i] = NULL;
}
}
}

int terminableSize;
trieNode *children[26];
};

class WordDictionary {
public:
WordDictionary() : root(new trieNode) {}

size_t Index(char c) {
return static_cast<size_t>(c % 26);
}

// Adds a word into the data structure.
void addWord(string word) {
// Write your code here
trieNode *cur = root;
for (size_t i = 0; i < word.size(); ++i) {
size_t idx = Index(word[i]);
if (!cur->children[idx]) {
cur->children[idx] = new trieNode;
}
cur = cur->children[idx];
}
++cur->terminableSize;
}

// 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_dfs(word, root);
}

bool search_dfs(string word, trieNode *cur) {
if (word.size() == 0 && cur->terminableSize > 0)
return true;
for (size_t i = 0; i < word.size(); ++i) {
if (word[i] == '.') {
for (size_t j = 0; j < 26; ++j) {
if (cur->children[j] && search_dfs(word.substr(i + 1), cur->children[j]))
return true;
}
return false;
}
else {
size_t idx = Index(word[i]);
if (!cur->children[idx])
return false;
cur = cur->children[idx];
}
}
if (cur->terminableSize > 0)
return true;
return false;
}

private:

trieNode *root;
};

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