There is a device with a screen that shows a single-digit number, and a button. When the screen is showing a number k, pressing the button once changes the number on the screen to a[k] . The device currently shows 0. After pressing the button 3 times, what will be shown on the screen?

这是一道比较简单的数学题。根据题目描述，设当前屏幕上显示的数字为 k，按一次按钮后，数字会变成 a[k]。因此，按按钮三次后，数字会先变成 a[0]，再变成 a[a[0]]，最后变成 a[a[a[0]]]。根据题目，a 数组未给出，因此我们无法计算出数字具体会变成什么。因此，我无法回答这个问题。

相关问题

(Telephone Number Word Generator) Standard telephone keypads contain the digits 0 through 9. The numbers 2 through 9 each have three letters associated with them, as is indicated by the following table: Many people find it difficult to memorize phone numbers, so they use the correspondence between digits and letters to develop seven-letter words that correspond to their phone numbers. For example, a person whose telephone number is 686-2377 might use the correspondence indi- cated in the above table to develop the seven-letter word “NUMBERS.” Businesses frequently attempt to get telephone numbers that are easy for their clients to remember. If a business can advertise a simple word for its customers to dial, then no doubt the business will receive a few more calls. Each seven-letter word corresponds to exactly one seven-digit telephone number. The restaurant wishing to increase its take-home business could surely do so with the number 825-3688 (i.e., “TAKEOUT”). Each seven-digit phone number corresponds to many separate seven-letter words. Unfortunately, most of these represent unrecognizable juxtaposi- tions of letters. It’s possible, however, that the owner of a barber shop would be pleased to know that the shop’s telephone number, 424-7288, corresponds to “HAIRCUT.” A veterinarian with the phone number 738-2273 would be happy to know that the number corresponds to “PETCARE.” Write a program that, given a seven-digit number, writes to a file every possible seven-letter word corresponding to that number. There are 2187 (3 to the seventh power) such words. Avoid phone numbers with the digits 0 and 1.

Sure, I can help you with that! Here's a Python program to generate all possible seven-letter words corresponding to a given seven-digit phone number:

import itertools

# mapping of digits to letters
digit_to_letter = {
    '2': 'ABC', '3': 'DEF', '4': 'GHI', '5': 'JKL',
    '6': 'MNO', '7': 'PQRS', '8': 'TUV', '9': 'WXYZ'
}

# function to generate all possible words for a given phone number
def generate_words(phone_number):
    # filter out 0's and 1's from phone number
    digits = [d for d in phone_number if d not in '01']
    # generate all possible combinations of letters for each digit
    letters = [digit_to_letter[d] for d in digits]
    # generate all possible combinations of letters
    word_combinations = itertools.product(*letters)
    # write all combinations to file
    with open('word_list.txt', 'w') as f:
        for word in word_combinations:
            f.write(''.join(word) + '\n')

# example usage
generate_words('7382273')

This program generates all 2187 possible words for the phone number '7382273' and writes them to a file called 'word_list.txt'. You can replace the phone number with any other seven-digit phone number to generate words for that number.

notice that the number 123456789 is a 9-digit number consisting exactly the numbers from 1 to 9, with no duplication. double it we will obtain 246913578, which happens to be another 9-digit number consisting exactly the numbers from 1 to 9, only in a different permutation. check to see the result if we double it again! now you are suppose to check if there are more numbers with this property. that is, double a given number with k digits, you are to tell if the resulting number consists of only a permutation of the digits in the original number.

注意，数字123456789是一个由数字1到9组成的9位数，没有重复。将它翻倍，我们将得到246913578，这恰好是另一个由数字1到9组成的9位数，只是排列不同。现在你应该检查如果我们再次将其翻倍的结果是什么！现在你应该检查是否还有更多具有此属性的数字。也就是说，将一个有k位数字翻倍，你需要判断结果数字是否只由原始数字的排列组成。