Leetcode 211. Design Add and Search Words Data Structure

Design a data structure supporting addWord(word) and search(pattern) where '.' in the pattern matches any single letter; the core challenge is efficient pattern matching with wildcards, typically solved with a trie plus DFS/backtracking on '.' nodes. Expect up to 10^4 operations and word length ≤ 25, so trie-based solutions meet the performance constraints.