def update_state(self, state_arr, action_arr):
        '''
        Update state.
        
        Override.

        Args:
            state_arr:    `np.ndarray` of state in `self.t`.
            action_arr:   `np.ndarray` of action in `self.t`.
        
        Returns:
            `np.ndarray` of state in `self.t+1`.
        '''
        x, y = np.where(action_arr[-1] == 1)
        self.__agent_pos = (x[0], y[0])
        self.__route_memory_list.append((x[0], y[0]))
        self.__route_long_memory_list.append((x[0], y[0]))
        self.__route_long_memory_list = list(set(self.__route_long_memory_list))
        while len(self.__route_memory_list) > self.__memory_num:
            self.__route_memory_list = self.__route_memory_list[1:]

        return self.extract_now_state()
Update state.
        
        Override.

        Args:
            state_arr:    `np.ndarray` of state in `self.t`.
            action_arr:   `np.ndarray` of action in `self.t`.
        
        Returns:
            `np.ndarray` of state in `self.t+1`.