(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 C++ 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 the C++ code to generate all possible seven-letter words for a given seven-digit phone number:

#include <iostream>
#include <fstream>
#include <string>
using namespace std;

// Function to generate all possible seven-letter words for a given phone number
void generateWords(string number, string word, int index, ofstream& outfile) {
    // Base case: all digits have been processed
    if (index == number.size()) {
        outfile << word << endl;  // write the word to the output file
        return;
    }

    // Generate all possible letters for the current digit
    string letters = "";
    switch (number[index]) {
        case '2':
            letters = "ABC";
            break;
        case '3':
            letters = "DEF";
            break;
        case '4':
            letters = "GHI";
            break;
        case '5':
            letters = "JKL";
            break;
        case '6':
            letters = "MNO";
            break;
        case '7':
            letters = "PQRS";
            break;
        case '8':
            letters = "TUV";
            break;
        case '9':
            letters = "WXYZ";
            break;
    }

    // Recursively generate words for the remaining digits
    for (int i = 0; i < letters.size(); i++) {
        generateWords(number, word + letters[i], index + 1, outfile);
    }
}

int main() {
    string number;
    cout << "Enter a seven-digit phone number (no 0's or 1's): ";
    cin >> number;

    // Open an output file to write the generated words
    ofstream outfile("words.txt");

    // Generate all possible seven-letter words
    generateWords(number, "", 0, outfile);

    // Close the output file
    outfile.close();

    cout << "Done! Check the output file 'words.txt' for the generated words." << endl;
    return 0;
}

To use this program, simply run it in a C++ compiler and enter a seven-digit phone number (without any 0's or 1's) when prompted. The program will generate all possible seven-letter words corresponding to that phone number and write them to a file called "words.txt".