Thread: Reverse of an integer

The problem:

Code:

The name of the function's name should be reverse. Let the 
name of its value parameter be x (which is an int).  The 
return datatype should be int.  Use the main() driver program 
provided below to test your function:

#include <iostream>
using namespace std;

// insert the reverse function here.

int main()
{
  int num;
  cin >> num;
  cout << "Reverse of " << num << " is " << reverse(num) << endl;
  return 0;
}

I know what I should do to obtain the reverse number, but its harder when using a function int. The program should handle any as much digits it can handle. So I know I should use a loop, and also you should know the number of digits - I've done that. My question is what is the proper way of returning the reverse digits. And by the way our lesson is about REFERENCES AND REFERENCE PARAMETER.

Use a modulo?then output the result side by side in a loop?

Reverse in what way? 43,621 => 12,634? 1 => -1? Sorry for sounding like a smart allec, but your goal seems ambiguous.

Example

Code:

#include <cstring>
#include <cstdlib>

int reverse(int number)
{
   char buffer[256];

   ssprintf(buffer, "&#37;d", number);
   return atoi(strrev(buffer));
}

Nothing too fancy... To be honest though, I am not sure if this is even what you are wanting to do.

I think Freddy steered you right. You want to figure out the number of digits represented, which you can do by progressively dividing by 10 (inside a loop)(incrementing a counter) until you return a zero. Once you know the number of digits, you can proceed accordingly. Looks like an interesting little task that is similar to reversing a string using the old array-of-characters manipulation.

And Prelude is right... some ints won't reverse as valid numbers, so you need to determine the size of an int and make sure that it won't overflow on reversing--whether you use strings or not.

Keith

You can tune a file system, but you can't tune a fish.

Only in this case, and I don't think Prelude was trying to scold anyone, per se.

Reversing a string also needs tweaking if the number is negative, ie:

Code:

if (number < 0) {
  strrev(result + 1);
} 
else {
  strrev(result);
}
return result;

But I'm only mentioning it since I'm not positive 8765- is correct.

#include <cstring>
#include <cstdlib>

int reverse(int number)
{
char buffer[256];

ssprintf(buffer, "&#37;d", number);
return atoi(strrev(buffer));
}

Using that is a lot better, but I cant really use that.

Code:

#include <iostream>
using namespace std;

// insert the reverse function here.

int main()
{
  int num;
  cin >> num;
  cout << "Reverse of " << num << " is " << reverse(num) << endl;
  return 0;
}

This is what we should use as our main. Then will just insert our function. I've done it using void, its "amatuerish",but at least I know how to do the logic part. And I think were required to use a function int, and so Im lost there. I have no idea how to properly return the digits in a loop.

Why can't you use that?

Code:

#include <iostream>
using namespace std;

// insert the reverse function here.

int main()
{
  int num;
  cin >> num;
  cout << "Reverse of " << num << " is " << reverse(num) << endl;
  return 0;
}

This should be our main

I know how to get the individual digits, but when using function I dont know how to return it properly using loop