Question

How to write a C++ program.

Additive persistence is a property of the sum of the digits of an integer. The sum of the digits is found, and then the summation of digits is performed creating a new sum. This process repeats until a single integer digit is reached. Consider the following example:

1. The beginning integer is 1234

2. Sum its digits is 1+2+3+4 = 10

3. The integer is now 10

4. The sum of its digits is 1 + 0 = 1

5. The integer is 1. When the value reaches a single digit, we are finished. This final integer is the additive root

Program Specifications

The program should run as follows.

1) Gather input as a redirection from a file input.txt. The program ends under one of the following circumstances a. the next gathered integer is a negative number. b. if all the integers from the file have been processed.

2) If the given integer is a single digit, report its additive persistence as 0 and its additive root as itself on a single line as two space separated numbers

3) For each multidigit, non-negative, integer output on a single line the two space separated numbers: a. the integer's additive persistence b. the integer's additive root

How to write a C++ program.

Answer 1

Code

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

void digSum(int n)
{
   int sum = 0;
  
   while(n > 0 || sum > 9)
   {
       if(n == 0)
       {
           n = sum;
           sum = 0;
       }
       sum += n % 10;
       n /= 10;
   }
   if(n==sum)
   cout <<"0 "<<sum<<endl;
   else
   cout <<"1 "<<sum<<endl;
}

int main() {

   //Create a dynamic array to hold the values
   vector<int> numbers;

   //Create an input file stream
   ifstream in("/Users/Akhilaperumalla/Desktop/readme.txt",ios::in);

   /*
As long as we haven't reached the end of the file, keep reading entries.
   */

   int number; //Variable to hold each number as it is read
  
//Read number using the extraction (>>) operator
while (in >> number) {
       //Add the number to the end of the array
       numbers.push_back(number);
   }

   //Close the file stream
   in.close();

   /*
   Now, the vector<int> object "numbers" contains both the array of numbers,
and its length (the number count from the file).
   */

   //Display the numbers
   cout << "Numbers:\n";
   for (int i=0; i<numbers.size(); i++) {
       if(numbers[i] < 0)
           break;
       else
           digSum(numbers[i]);
   }

   //cin.get(); //Keep program open until "enter" is pressed
   return 0;
}

Screenshot of input file

Screenshot of output: