0079 Word Search

Question

My Solution:

class Solution:
    def exist(self, board: List[List[str]], word: str) -> bool:
        ROWS, COLS = len(board), len(board[0])
        path = set()

        def backtrack(r, c, i):
            if i == len(word):
                return True
            
            if (r < 0 or c < 0 
                or r >= ROWS or c >= COLS
                or (r,c) in path
                or word[i] != board[r][c]):
                return False
            
            path.add((r,c))
            res = (backtrack(r, c+1, i+1) 
                or backtrack(r, c-1, i+1)
                or backtrack(r+1, c, i+1)
                or backtrack(r-1, c, i+1))
            path.remove((r,c))

            return res
        for r in range(ROWS):
            for c in range(COLS):
                if backtrack(r, c, 0):
                    return True

        return False