[Leetcode][python]Word Search/单词搜索

class Solution(object):
    def exist(self, board, word):
        """
        :type board: List[List[str]]
        :type word: str
        :rtype: bool
        """
        visited = [[False for j in range(len(board[0]))] for i in range(len(board))]

        for i in range(len(board)):
            for j in range(len(board[0])):
                if self.existRecu(board, word, 0, i, j, visited):
                    return True
        return False

    def existRecu(self, board, word, cur, i, j, visited):
        if cur == len(word):  # 如果到单词长度，结束。
            return True

        if i < 0 or i >= len(board) or j < 0 or j >= len(board[0]) or visited[i][j] or board[i][j] != word[cur]:
            return False  # 越界或者是当前字母不等于word中对应位置字母

        # 如果到这说明对应位置有，继续从此位置遍历四个方向
        visited[i][j] = True
        result = self.existRecu(board, word, cur + 1, i + 1, j, visited) or\
                 self.existRecu(board, word, cur + 1, i - 1, j, visited) or\
                 self.existRecu(board, word, cur + 1, i, j + 1, visited) or\
                 self.existRecu(board, word, cur + 1, i, j - 1, visited)         
        visited[i][j] = False

        return result