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Sep 29th, 2008

How do I convert an integer into digits and add their sum?

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I'm working on an assignment for Computer Science 121. The assignment is to write a program that prompts a user to input an integer and then outputs both the individual digits of the number and the sum of the digits. For example, it should output the individual digits of 3456 as 3 4 5 6 and the sum as 18. I can't seem to get it working properly; I think my algorithm is wrong. I tried rewriting the algorithm, but I keep getting stuck in it. Can someone help me out? Here's what I have so far:

C++ Syntax (Toggle Plain Text)
#include <iostream>
#include <cmath>
 
using namespace std;
 
int main()
{
	int num, num2, sum = 0, dig;
 
	cout << "Please enter a number" << endl;
	cin >> num;
 
	if(num < 0)
		num = -num;
	num2 = num;
	dig = num;
	do
	{
		do
		{
			dig = dig / 10;
		}
		while (dig >= 10);
 
		cout << dig << " ";
 
		if (num > 100)
			num = num - (100*(num/100));
		else
			num = num - (10*(num/10));
 
		sum = sum + num2 % 10;
 
		num2 = num2 / 10;
 
		dig = num;
 
	}
	while (num2 > 0);
	cout << endl;
	cout << "The sum of the digits is " << sum << endl;
 
	return 0;
}
#include <iostream>
#include <cmath>

using namespace std;

int main()
{
	int num, num2, sum = 0, dig;
	
	cout << "Please enter a number" << endl;
	cin >> num;
	
	if(num < 0)
		num = -num;
	num2 = num;
	dig = num;
	do
	{
		do
		{
			dig = dig / 10;
		}
		while (dig >= 10);

		cout << dig << " ";

		if (num > 100)
			num = num - (100*(num/100));
		else
			num = num - (10*(num/10));

		sum = sum + num2 % 10;

		num2 = num2 / 10;

		dig = num;

	}
	while (num2 > 0);
	cout << endl;
	cout << "The sum of the digits is " << sum << endl;

	return 0;
}

Thank you for the help

Last edited by ShadowOfBlood; Sep 29th, 2008 at 2:03 pm.

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ShadowOfBlood

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Sep 29th, 2008

Re: How do I convert an integer into digits and add their sum?

A combination of modulus division and normal division will do this nicely for you.

You have way to many steps, you can retreive each number in 1 line of code using both normal and modulus division.

its all to do with 10^x in a way xD

Chris

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Sep 29th, 2008

Re: How do I convert an integer into digits and add their sum?

Start with the summation, because that's easy. You already seem to know about taking the remainder of ten to get the least significant digit and dividing by ten to slice it off. Remember to keep it as simple as possible. When you do this with more than one loop, you're not keeping it simple:

C++ Syntax (Toggle Plain Text)
#include <iostream>
 
int main()
{
  std::cout<<"Enter a number: ";
 
  int num;
 
  if ( std::cin>> num ) {
    int sum = 0;
 
    if ( num < 0 )
      num = -num;
 
    while ( num != 0 ) {
      sum += num % 10;
      num /= 10;
    }
 
    std::cout<<"The sum is "<< sum <<'\n';
  }
}
#include <iostream>

int main()
{
  std::cout<<"Enter a number: ";

  int num;

  if ( std::cin>> num ) {
    int sum = 0;

    if ( num < 0 )
      num = -num;

    while ( num != 0 ) {
      sum += num % 10;
      num /= 10;
    }

    std::cout<<"The sum is "<< sum <<'\n';
  }
}

The fun part is getting the digits to print out from most significant to least significant, as per your example using 3456. If you just print num % 10 in the while loop, you can get the digits in reverse. To print in the right order, you need to store the digits somewhere (the simpler solution, IMO), or extract the digits from most significant to least significant.

Narue

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Sep 29th, 2008

Re: How do I convert an integer into digits and add their sum?

Thanks, I'll try it

Last edited by ShadowOfBlood; Sep 29th, 2008 at 2:10 pm.

ShadowOfBlood

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Sep 29th, 2008

Re: How do I convert an integer into digits and add their sum?

Quote originally posted by Narue ...

The fun part is getting the digits to print out from most significant to least significant, as per your example using 3456. If you just print num % 10 in the while loop, you can get the digits in reverse. To print in the right order, you need to store the digits somewhere (the simpler solution, IMO), or extract the digits from most significant to least significant.

This is what i was thinking about from the go was to get them in the correct order, so maybe my post may give you a small clue

Freaky_Chris

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Sep 29th, 2008

Re: How do I convert an integer into digits and add their sum?

Thanks for the help, but I still can't seem to grasp how to output the digits in order. I can get them to output in reverse just fine, but when I try to get them to output in order I can't seem to figure it out. I just started learning c++ and just learned loops, so I don't know much code. Can I get some more clues? My Computer Science class starts in 15 minutes (last minute, I know >< Thought I could figure it out on my own).

ShadowOfBlood

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Sep 29th, 2008

Re: How do I convert an integer into digits and add their sum?

You could store all the numbers in an array as suggested and then print them out, or you can do something like this...

num = 546

mostsigdigit = (546 % 10^3)/10^2

probably gave too much away there but oh well

Freaky_Chris

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Sep 29th, 2008

Re: How do I convert an integer into digits and add their sum?

But what if the user enters a number with more than 3 digits?

Oh, and I haven't learned arrays yet :\

Last edited by ShadowOfBlood; Sep 29th, 2008 at 2:43 pm.

ShadowOfBlood

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Sep 29th, 2008

Re: How do I convert an integer into digits and add their sum?

Thanks for the help

I have to get to class now.

ShadowOfBlood

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Sep 29th, 2008

Re: How do I convert an integer into digits and add their sum?

Well it would be

(546 % 10^x)/10^(x-1)

where x = number of digits in number

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