EOJ-自适应编程学习平台

On a standard telephone keypad, the digits are mapped onto the alphabet (minus the letters Q and Z) as shown in this diagram:

In order to make their phone numbers more memorable, service providers like to find numbers that spell out some word appropriate to their business that makes that phone number easier to remember. Such words that help you remember some other data are called mnemonics. Write a function ListMnemonics that generates all possible letter combinations that correspond to a given number, represented as a string of digits. For example, if you call ListMnemonics (“723”) your program should generate the 27 possible letter combinations corresponding to that prefix, as follows:

If the argument passed to ListMnemonics contains a 0 or a 1, that position in the output should simple be displayed as the digit, since there are no letters that correspond to it. For example, if you used the function to generate mnemonics for the area code 415, you program should generate the following nine strings:

A string with three digits

All mnemonics with alphabetical order, one mnemonic in one line