Merge pull request neetcode-gh#86 from Pegasus02K/patch-10

Create 211-Design-Add-and-Search-Words-Data-Structure.cpp

Author: neetcode-gh

cpp/211-Design-Add-and-Search-Words-Data-Structure.cpp

@@ -0,0 +1,64 @@
+struct TrieNode {
+	TrieNode* children[26];
+	bool isWordEnd;
+
+	TrieNode() : isWordEnd(false) {
+		for (int i = 0; i < 26; ++i)
+			children[i] = nullptr;
+	}
+};
+
+class WordDictionary {
+private:
+	TrieNode* root;
+public:
+	WordDictionary() {
+		root = new TrieNode;
+	}
+
+	void addWord(string word) {
+		// simple trie insertion
+		TrieNode* cur = root;
+
+		int idx;
+		for (int i = 0; i < word.size(); ++i) {
+			idx = word[i] - 'a';
+			if (cur->children[idx] == nullptr)
+				cur->children[idx] = new TrieNode;
+			cur = cur->children[idx];
+		}
+		// mark the last node as end of a word
+		cur->isWordEnd = true;
+	}
+
+	bool recursiveSearch(const string &word, int curIdx, const TrieNode *node) {
+		auto cur = node;
+
+		for (int i = curIdx; i < word.size(); ++i) {
+			if (word[i] == '.') {
+				// can match any character - backtracking is required
+				for (int j = 0; j < 26; ++j) {
+					if (cur->children[j] == nullptr) // skip non-existing characters
+						continue;
+					if (recursiveSearch(word, i + 1, cur->children[j])) // try and backtrack if fails
+						return true;
+				}
+				// search with backtracking failed in all children
+				return false;
+			}
+			else {
+				// simple trie search
+				int idx = word[i] - 'a';
+				if (cur->children[idx] == nullptr)
+					return false;
+				cur = cur->children[idx];
+			}
+		}
+		// check if the node is end of any word
+		return cur->isWordEnd;
+	}
+
+	bool search(string word) {
+		return recursiveSearch(word, 0, root);
+	}
+};