Need help writing c++ with using recursion (intro c++) Attempt inside.

[sam0617]

Hello. I've tried to do this on my own over the weekend but it's really confusing. How would I go about making a recursive function which is my 'int evenUp ( int number )' to add 1 to each of my even digits?

The program will create a new number found by increasing each even digit of user's number by 1. Then the program will output the difference of the new number subtract the old number.

Example:
Enter a number: 3456
3557 - 3456 = 101

Here's what I have so far:


#include <iostream>
using namespace std;

int getNumber()
{
int num;
cout << "Enter a number: ";
cin >> num;
return num;
}


int evenUp (int number)
{
if ( number < 10 && number%2 == 1 ) return number;
int a_digit = number % 10; //stores last digit of the number
if ( a_digit%10 == 0) {
a_digit = a_digit+1;
return a_digit + number/10;
}
}






int main()
{
int number = getNumber();
int evenUpNumber = evenUp( number );

cout << evenUpNumber << " - " << number << " = " << evenUpNumber - number << endl;
system("Pause");
return 0;
}


As you can see my recursion function 'int evenUp (int number)' is wrong but I can't figure out how to fix it.
Any help would be appreciated. Thank you.

[sandrorb]

Hi Sir,

In order to help you I need to understand more what this function eventUp is intended to do.

Can you explain me what this function is about?

[]'s

Sandro Boschetti.

[sam0617]

Hello Sir Sandrorb,


int evenUp (int number) is supposed to take the number the user put in and for every even digit, the function will add 1 to it then return it so I can use it in int main.

So for example, if number is 323, it should return 424.

Thank you for any help.

[sandrorb]

Based on what you said, the function should be:

int evenUp (int number){
if ( number % 2 != 0) {
return number + 1;
}
return number;
}

Right?

[sam0617]

Let me try. I'm going to kick myself if it was that easy.

[sam0617]

Nope, it gives me this:

Input: 323
output: 324 - 323 = 1

when it should be
Input: 323
output: 424 - 323 = 101

Thank you anyway, good sir.

[sandrorb]

I'm probably not understanding your needs.

Do you need a function that return the first even number from the entered number + 100?

Like this?

int evenUp (int number){
if ( (number + 100) % 2 != 0) {
return number + 100 + 1;
}
return number + 100;
}

[sam0617]

The program is supposed to prompt the user for an integer number.

Then it will take that number and find every even digit and add 1 to it.

So for instance:
User puts in: 323

int evenUp (int number) should make it so that each even digit in 323 will add 1 to it and return 424.

Another example is:
User puts in: 5234
it will return: 5335 because every even digit in 5234 had 1 added to it.

[sandrorb]

I'm sorry. I think now I understand what you need.

I am thinking over to find out a solution. As sson as I get it, I post it here.

[sam0617]

I'm sorry to bother you, sandrorb.

[sandrorb]

Not at all. It's a good puzzle to be up to date.

[sam0617]

Heh. I'm trying out different codes.

Here's what my professor sent me as a hint.


What I have understood from your description and your code;
First You will need to get each digit from your number separately.
Here is how You can get it :
Number is 323.
a_digit = 323 % 10 //(% == Mod)
//a_digit now contains 3; You can even check it here and increase or whatever u like
Number = 323 / 10
//Number will now contain 32


So using other names, here's the same thing as above, written differently
{
a_digit = Number % 10 // a_digit = 2
// Increase digit and store digit if odd etc.
Number = Number / 10 // Number = 3
}


I just can't figure out how to increase by 1 and return it

[sandrorb]

Almost there. The digits are inverted and I'm not using recursivity.

int evenUp (int number){

int i = 1;
int digit;
int newNumber = 0;

while ( number > 0){
digit = number % 10;
cout << digit;
number = number / 10;
if (digit % 2 != 0) {
if (digit == 9){
digit = 0;
} else {
digit = digit + 1;
}
}
newNumber = newNumber * 10 + digit ;
i++;
}

return newNumber;
}

[sam0617]

Hey Sandrorb, I figured it out.

Here it is just incase you're curious. Thank you so much for your help but it had to use recursion.



#include <iostream>
using namespace std;


/**
* This function asks the user for a number.
*
* Parameter: None
* Return: Number enter by user.
*/
int getNumber()
{
int num;
cout << "Enter a number: ";
cin >> num;
return num;
}

/**
* This function takes the number and adds 1 to all even digits
*
* Parameter: integer number given in getNumber()
* Return: Returns a number where all the even digits are added by 1
*/
int evenUp (int number)

{
if ( number < 10 )
{
if ( number % 2 != 0 ) return number;
return number + 1;
}
int digitA = evenUp(number%10);
return evenUp( number / 10 ) * 10 + digitA;
}


/**
* This function prints out the difference
* between the new number and the original number
*
*/
int main()
{
int number = getNumber();
int evenUpNumber = evenUp( number );

cout << evenUpNumber << " - " << number << " = " << evenUpNumber - number << endl;
system("Pause");
return 0;
}

[sandrorb]

You're welcome!

[sandrorb]

Don't you think you should change (number % 2 != 0) to number % 2 == 0)?

[sandrorb]

In your algorithm if you enter a number like 1929 the result is 3030. Is the correct?
I guess you should take care of digit 9.

[sandrorb]

Even though you have said recursion is mandatory, just for a sake of curiosity, I post this code below:


int evenUp (int number){

int i = 0;
int digit;
int newNumber = 0;

while ( number > 0){
digit = number % 10;
number = number / 10;
if (digit % 2 != 0) {
if (digit == 9){
digit = 0;
} else {
digit = digit + 1;
}
}
newNumber = newNumber + pow(10, i) * digit;
i++;
}

return newNumber;
}

[bluecoder]

soory for the lack of knowledge ,, but i think that the recursive function is not working properly .
can you please elobrate on the function .

[sandrorb]

What recursive function? That one by sam0617?
I suppose the only thing wrong with that function is how it treats the digit nine.