Find all dictionary words in a grid

You are given: - A 2D grid of characters `board` with `m` rows and `n` columns. - A list of strings `words` (a dictionary). A word can be formed by starting from any cell and moving to **adjacent** cells (up, down, left, right). Each cell may be used **at most once** in forming a single word. Return **all distinct** words from `words` that can be formed in the grid. ### Input - `board`: `m x n` array of lowercase letters. - `words`: list of lowercase strings. ### Output - A list (or set) of all dictionary words that appear in the board. ### Constraints (reasonable interview constraints) - `1 <= m, n <= 12` - `1 <= len(words) <= 3 * 10^4` - `1 <= len(word) <= 10` - Letters are lowercase `a-z`. ### Notes - The interviewer hinted that a **trie (prefix tree)** is a common approach, but a **backtracking** solution is also acceptable if performance is addressed.