C++ FAQ - How to add the individual digits of a given number?

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To solve this problem, you need to do mod (modulus %) and  division (/) operations in a for loop until you reach single digit.

Look at the sample code and output! It is easy to understand.

Source Code

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#include <iostream>

#include <tchar.h>

 

// Adding the individual digits of a given number

int _tmain(int argc, _TCHAR* argv[])

{

    while(1)

    {

        int input = 0;

 

        std::cout << "\nEnter a number (-1 to exit): ";

        std::cin >> input;

 

        if( input < 0)

            break;

 

        int sum = 0;

        int j = 0;

        for(; input >= 10; j++)

        {

            sum += input % 10;

            input = (input / 10);

        }

        sum += input;

        j++;

        std::cout << "Number of digits: " << j;

        std::cout << "\tSum of digits: " << sum;

        std::cout << "\n\n";

    }

   

    return 0;

}

 

Output

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Enter a number (-1 to exit): 100

Number of digits: 3     Sum of digits: 1

 

 

Enter a number (-1 to exit): 123

Number of digits: 3     Sum of digits: 6

 

 

Enter a number (-1 to exit): 555

Number of digits: 3     Sum of digits: 15

 

 

Enter a number (-1 to exit): 6666

Number of digits: 4     Sum of digits: 24

 

 

Enter a number (-1 to exit): 88888

Number of digits: 5     Sum of digits: 40

  

Enter a number (-1 to exit): -1

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