LeetCode-211.Add and Search Word - Data structure design_worddictionary leetcode-优快云博客

本文链接：https://blog.youkuaiyun.com/zmq570235977/article/details/51924261

本文介绍使用Trie树数据结构实现支持单词添加与搜索功能的词典，其中包括对正则表达式的匹配支持。通过递归方法实现了对含有通配符'.'的字符串的搜索。

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

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.

显然这是一道Trie树的应用

关于Trie树的构造可以查看题 LeetCode-208.Implement Trie (Prefix Tree)

查找".ad"和"b.."等非完整词时，需要用到递归

class TrieNode
{
public:
	TrieNode *children[26];
	bool isWord;
	TrieNode()
	{
		isWord = false;
		for (auto &node : children)
			node = NULL;
	}
};

class WordDictionary {
public:
    WordDictionary()
	{
		root = new TrieNode();
	}
    // Adds a word into the data structure.
    void addWord(string word) {
        TrieNode *node = root;
		for (char c : word)
		{
			if (!node->children[c - 'a'])
				node->children[c - 'a'] = new TrieNode();
			node = node->children[c - '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.
    bool search(string word)
    {
        return search2(word, root);
    }
    
private:
	TrieNode* root;
	bool search2(string word, TrieNode *pp)
	{
		TrieNode *node = pp;
		for (char c : word)
		{
			if (c == '.')
			{
				for (auto &p : node->children)
				{
					if (!p)
						continue;
					if (search2(word.substr(1), p))
						return true;
				}
				return false;
			}
			else
			{
				if (!node->children[c - 'a'])
					return false;
				return search2(word.substr(1), node->children[c - 'a']);
			}
		}
		return node->isWord;
	}
};

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