Question

I’m trying to learn c++ on my own and I’ve hit a bit of a road block. The problem is I need to take an integer,split it into its digits and get the sum of the digits and display them.

Example:

input number: 123456
digits in the integer: 1 2 3 4 5 6
sum: 21

I have it all done, but when I rip the integer, into digits I can’t display it correctly. It displays in reverse order.

So in the program below I enter 1234 and it spits out 4 3 2 1. I know why, I just don’t know how to fix it.

Here is my code so far:

#include "stdafx.h"
#include <cstdlib>
#include <iostream>
#include <math.h>

int countDigitsInInteger(int n)
{
    int count =0;
    while(n>0)
    {
       count++;
       n=n/10;
    }
    return count;
}

using namespace std;

int main(int argc, char *argv[])
{  
    int intLength =0;
    int number;
    int digit;      
    int sum = 0;
    string s;    
    cout << "Please enter an integer ";
    cin >>number;
    cout << "Orginal Number = "<<number <<endl;
    //make the number positive
    if (number<0)
    number = -number;    
    intLength = countDigitsInInteger(number);
    //break apart the integer into digits
    while(number>0)
    {                         
        digit = number % 10;
        number = number / 10;        
        cout <<digit << " "; 
        sum = sum+digit; 
    } 
    cout <<endl <<"Sum of the digits is: "<<sum<<endl;
    system("PAUSE");
    return EXIT_SUCCESS;
}

Here is my solution

can’t see 🙂

Answer 1

Your problem comes from the fact that you are reading the digits backwards, thus you need to print them out backwards. A stack will help you tremendously.

#include "stdafx.h"
#include <cstdlib>
#include <iostream>
#include <math.h>
#include <stack>

int countDigitsInInteger(int n)
{
    int count =0;
    while(n>0)
    {
        count++;
        n=n/10;
    }
    return count;
}

using namespace std;

int main(int argc, char *argv[])
{  
    int intLength =0;
    int number;
    int digit;      
    int sum = 0;
    string s;    
    cout << "Please enter an integer ";
    cin >>number;
    cout << "Orginal Number = "<<number <<endl;
    //make the number positive
    if (number<0)
        number = -number;    

    intLength = countDigitsInInteger(number);
    //break apart the integer into digits

    stack<int> digitstack;
    while(number>0)
    {                         
        digit = number % 10;
        number = number / 10;
        digitstack.push(digit);
        sum = sum+digit; 
    }

    while(digitstack.size() > 0)
    {
        cout << digitstack.top() << " ";
        digitstack.pop();
    }

    cout <<endl <<"Sum of the digits is: "<<sum<<endl;
    system("PAUSE");
    return EXIT_SUCCESS;
}

Oh, and BTW, keep your indentation clean. Its important.

EDIT: In response to Steve Townsend, this method is not necessarily overkill, it is just different from yours. The code can be slimmed down so that it seems less like overkill:

#include <iostream>
#include <stack>
#include <string>

using namespace std;

int getInput(string prompt)
{
    int val;
    cout << prompt;
    cin >> val;
    return val < 0 ? -val : val;
}

int main(int argc, char** argv)
{
    int num = getInput("Enter a number: ");
    cout << "Original Number: " << num << endl;

    stack<int> digits;
    int sum = 0;
    while(num > 0)
    {
        digits.push(num % 10);
        sum += digits.top();
        num = num / 10;
    }

    while(digits.size() > 0)
    {
        cout << digits.top() << " ";
        digits.pop();
    }

    cout << endl << "Sum of digits is " << sum << endl;

    return 0;
}