Word Search II (find all words on board)

Problem: Find All Words in a Grid (Word Search II) Given an m x n character grid board and an array of strings words, return all words from words that can be found in the grid. Matching rules A word is constructed from letters of sequentially adjacent cells. Adjacent means up, down, left, right (no diagonals). The same cell may not be used more than once in a single word. Output Return all found words (each word at most once). Order does not matter. Constraints (common setting) 1 <= m, n <= 12 1 <= words.length <= 3 * 10^4 1 <= words[i].length <= 10 board[i][j] are lowercase letters words[i] are lowercase letters Example Input: board = [["o","a","a","n"],["e","t","a","e"],["i","h","k","r"],["i","f","l","v"]] words = ["oath","pea","eat","rain"] Output: ["eat","oath"] Example Input 4 4 o a a n e t a e i h k r i f l v 4 oath pea eat rain Output eat oath