211 Add and Search Word - Data structure design

Author: int32bit

algorithms/AddandSearchWord/README.md

@@ -0,0 +1,63 @@
+## 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`.
+
+click to show hint.
+
+You should be familiar with how a Trie works. If not, please work on this problem: [Implement Trie (Prefix Tree)](../ImplementTrie) first.
+
+## Solution
+
+Trie树的扩展，如果搜索字符，和Trie树一样，若为".", 则DFS之
+
+```cpp
+bool search(TrieNode *p, const char *target) const {
+			if (p == nullptr)
+				return false;
+			int len = strlen(target);
+			if (target == nullptr || len == 0) { // 到底单词尾部
+				return p->exist;
+			}
+			char c = *target;
+			if (c != '.') { // 字符不是"."
+				int index = c - 'a';
+				return search(p->children[index], target + 1);
+			} else { // 字符是".", DFS
+				for (int i = 0; i < TrieNode::SPACE_SIZE; ++i) {
+					if (search(p->children[i], target + 1))
+						return true;
+				}
+				return false;
+			}
+		}
+```
+
+搜索单词`word`, 只需要调用`search(root, word.c_str())`即可.
+
+## 扩展
+
+[Implement Trie (Prefix Tree)](../ImplementTrie): Trie树实现

algorithms/AddandSearchWord/trie.cpp

@@ -0,0 +1,78 @@
+#include <cstdio>
+#include <string>
+#include <cstdlib>
+#include <vector>
+#include <iostream>
+#include <cstring>
+using namespace std;
+class TrieNode {
+	public:
+		static const int SPACE_SIZE = 26;
+		TrieNode *children[SPACE_SIZE];
+		bool exist;
+
+		TrieNode() {
+			for (int i = 0; i < SPACE_SIZE; ++i) {
+				children[i] = nullptr;
+			}
+			exist = false;
+		}
+};
+class WordDictionary {
+	public:
+		WordDictionary() {
+			root = new TrieNode();
+		}
+		void addWord(const string s) {
+			TrieNode *p = root;
+			for (char c : s) {
+				int index = c - 'a';
+				if (p->children[index] == nullptr) {
+					p->children[index] = new TrieNode();
+				}
+				p = p->children[index];
+			}
+			p->exist = true;
+		}
+		void insert(const string s) {
+			addWord(s);
+		}
+		bool search(const string key) const {
+			return search(root, key.c_str());
+		}
+	private:
+		TrieNode *root;
+		bool search(TrieNode *p, const char *target) const {
+			if (p == nullptr)
+				return false;
+			int len = strlen(target);
+			if (target == nullptr || len == 0) {
+				return p->exist;
+			}
+			char c = *target;
+			if (c != '.') {
+				int index = c - 'a';
+				return search(p->children[index], target + 1);
+			} else {
+				for (int i = 0; i < TrieNode::SPACE_SIZE; ++i) {
+					if (search(p->children[i], target + 1))
+						return true;
+				}
+				return false;
+			}
+		}
+};
+int main(int argc, char **argv)
+{
+	WordDictionary trie;
+	trie.insert("bad");
+	trie.insert("dad");
+	trie.insert("mad");
+	cout << trie.search("") << endl;
+	cout << trie.search("pad") << endl;
+	cout << trie.search("bad") << endl;;
+	cout << trie.search(".ad") << endl;
+	cout << trie.search("b..") << endl;
+	cout << trie.search("mada") << endl;
+	return 0;
+}

algorithms/ImplementTrie/README.md

@@ -63,3 +63,6 @@ class Trie {
 		TrieNode *root;
 };
 ```
+## 扩展
+
+[Add and Search Word - Data structure design](../AddandSearchWord): 实现含有任意字符的搜索