Question

Write a program in C++ that, given a seven-digit number, writes to a file every possible seven-letter corresponding to that number. There are 2187 (3 to the seventh power) such words.

Include the numbers 0 and 1; just embed them in the words as a 0 and a 1. Example: one possibility for 5701679 would be: LR01OPW. Assume the user correctly enters only 7 digits (no ‘-‘). Read the user input into a char array. Use a recursive function to build the combinations. Leave the output in a file and inform the user of the file name before exiting.

You will need some constants:

const int ROWSIZE = 10;

const int COLSIZE = 5;

const int NUMSIZE = 8;

You will need an array to read in the user’s 7-digit number, a 2-dimensional character array, and an array in which to build the number combinations:char array[NUMSIZE]; // user input – do not go beyond 7 chars and a null byte!

// 2-d array of letters

char letters[ROWSIZE][COLSIZE] = { { '0', '\0', '\0', '\0', '\0' },

{ '1', '\0', '\0', '\0', '\0' },

{ 'A', 'B', 'C', '\0', '\0' },

{ 'D', 'E', 'F', '\0', '\0' },

{ 'G', 'H', 'I', '\0', '\0' },

{ 'J', 'K', 'L', '\0', '\0' },

{ 'M', 'N', 'O', '\0', '\0' },

{ 'P', 'Q', 'R', 'S', '\0' },

{ 'T', 'U', 'V', '\0', '\0' },

{ 'W', 'X', 'Y', 'Z', '\0' } };

char buildArr[ROWSIZE]; // output

Your recursive routine should have five parameters:

void combine (char *, // user input array

char [ROWSIZE][COLSIZE], // 2-d array of letters

char *, // array in which to build the output

int, // index into output array

ofstream&); // reference to the open output file

Please include comments

Answer 1

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

const int ROWSIZE = 10;
const int COLSIZE = 5;
const int NUMSIZE = 8;

void combine(char *array, char letters[ROWSIZE][COLSIZE], char *build_array, int n, ofstream& output) 
{

/******************************************************************** 
 char* is for user input
 char is for 2D array of letters
 char* is for an array in which to build the output
 int is for index into output array
*********************************************************************/

        if (n == NUMSIZE - 1) {
                output << build_array << endl;
                return;
        }
        else {
                int c = 0;      // counter to move through columns in 2-D array
                int b = array[n] - '0'; // counter to move through rows in 2-D array
                
                while (letters[b][c] != '\0') {
                        build_array[n] = letters[b][c++];
                        combine(array, letters, build_array, n + 1, output);
                }
        }
}

int main() 
{
        char array[NUMSIZE];    // array
        char buildArr[ROWSIZE] = { 0 }; // array
        int z = 0;      // counter to function
        ofstream os;    // output file

        cout << "Enter a seven digit number: "; 
        cin >> array; 
        cout << endl;

        os.open("combination.txt");

        if (!os.is_open())
                cout << "ERROR 0504: Unable to execute file. ";

        char letter[ROWSIZE][COLSIZE] = {{ '0', '\0', '\0', '\0', '\0' },
                                                                         { '1', '\0', '\0', '\0', '\0' },
                                                                         { 'A', 'B', 'C', '\0', '\0' },
                                                                         { 'D', 'E', 'F', '\0', '\0' },
                                                                         { 'G', 'H', 'I', '\0', '\0' },
                                                                         { 'J', 'K', 'L', '\0', '\0' },
                                                                         { 'M', 'N', 'O', '\0', '\0' },
                                                                         { 'P', 'Q', 'R', 'S', '\0' },
                                                                         { 'T', 'U', 'V', '\0', '\0' },
                                                                         { 'W', 'X', 'Y', 'Z', '\0' }};

        combine(array, letter, buildArr, z, os);

        cout << "\nFilename: combination.txt" << endl;
        os.close();
        return 0;
}