【leetcode】79. 单词搜索

class Solution:
    def exist(self, board: List[List[str]], word: str) -> bool:
        result = False
        directions = [(0,1), (0,-1), (-1,0), (1,0)]
        def next_in(i,j,k):            
            if k == wl-1 and board[i][j] == word[k]:
                return True

            result = False
            for direction in directions:
                new_i = i + direction[0]
                new_j = j + direction[1]
                new_k = k + 1
                if 0 <= new_i < rm and 0 <= new_j < rl:
                    if board[new_i][new_j] == word[new_k]:
                        if ((new_i,new_j) not in locations):
                            locations.add((i,j))
                            if next_in(new_i,new_j,new_k):
                                return True
                            else:
                                locations.remove((i,j))
                        
            return result                        

        k = 0
        rm = len(board)
        rl = len(board[0])
        wl = len(word)
        locations = set()
        for i in range(len(board)):
            for j in range(len(board[i])):
                if board[i][j] == word[k]:
                    if next_in(i,j,k):
                        return True

        return result