波波老司，觉得逻辑没有错啊，就是递归不出结果（python3）

class Solution(object):

    res = []
    used = []

    def ninegong(self,i, j, board, num): #判断当前9宫是否包含此数字
        hang = int(i / 3)
        lie = int(j / 3)
        for h in range(hang*3, hang*3 + 3):
            for l in range(lie*3, lie*3 + 3):
                if board[h][l] == str(num):
                    return True
        return False

    def hang(self, i, board, num): #行不包括此数字
        return str(num) in board[i]

    def lie(self, j, borad, num): #列不包括此数字
        return str(num) in [exm[j] for exm in borad]

    def putSudo(self, borad, row, col):
        if row == col:
            self.res.append(borad)
            return True
        for j in range(col):
            if borad[row][j] != '.':
                continue
            for k in range(1, col + 1):
                if self.used[row][j] == False and self.hang(row, borad, k) == False and self.lie(j, borad, k) == False and self.ninegong(row, j, borad, k) == False:
                    self.used[row][j] = True
                    borad[row][j] = str(k)
                    if self.putSudo(borad, row + 1, col):
                        return True
                    borad[row][j] = '.'
                    self.used[row][j] = False
            return False
        return True # 这里不确定返回True还是False 貌似true是有解的

    def solveSudoku(self, board):
        """
        :type board: List[List[str]]
        :rtype: None Do not return anything, modify board in-place instead.
        """
        self.res = []
        row = len(board)
        if row < 1:
            return []
        col = len(board[0])
        self.used = [[False]*row for i in range(col)]
        for i in range(row):
            for j in range(col):
                if board[i][j] == '.':
                    continue
                self.used[i][j] = True
        self.putSudo(board, 0, col)
        return self.res[0]