0079 Word Search

class Solution:    def __init__(self):    def neighbors(self, board, visited, point):        [row, col] = point        neighbor = []        if row > 0 and not visited[row - 1][col]:            neighbor.append([row-1, col])        if row < len(board) - 1  and not visited[row+1][col]:            neighbor.append([row+1, col])        if col > 0 and not visited[row][col-1]:            neighbor.append([row, col-1])        if col < len(board[row]) - 1 and not visited[row][col+1]:            neighbor.append([row, col+1])        return neighbor
    def dfs(self, board, visited, word, current, candidates):        [current_row, current_col] = current        visited[current_row][current_col] = True        if not word:            return True        for candidate in candidates:            [x, y] = candidate            if not visited[x][y] and word[0] == board[x][y]:                visited[x][y] = True                neighbor = self.neighbors(board, visited, candidate)                if not self.dfs(board, visited, word[1:], candidate, neighbor):                    continue                return True        visited[current_row][current_col] = False        return False
    def exist(self, board: List[List[str]], word: str) -> bool:        rows = len(board)        cols = len(board[0])
        graphCount = dict()        wordCount = collections.Counter(word)        for i in range(rows):            for j in range(cols):                graphCount[board[i][j]] = graphCount.get(board[i][j], 0) + 1
        for key,val in wordCount.items():            if key not in graphCount:                return False
            if val > graphCount[key]:                return False
        starting_points = []        for x, vx in enumerate(board):            for y, vy in enumerate(board[x]):                if board[x][y] == word[0]:                    starting_points.append([x, y])
        for starting_point in starting_points:            visited = [[False for i in range(cols)] for j in range(rows)]            neighbor = self.neighbors(board, visited, starting_point)            if self.dfs(board, deepcopy(visited), word[1:], starting_point, neighbor):                return True            else:                continue        return False

rows = len(board)cols = len(board[0])graphCount = dict()wordCount = collections.Counter(word)for i in range(rows):    for j in range(cols):    graphCount[board[i][j]] = graphCount.get(board[i][j], 0) + 1    for key,val in wordCount.items():        if key not in graphCount:            return False        if val > graphCount[key]:            return False