Question

Is there a library function or easy way of reading a number backwards and operating with it? By operating, I mean do operations with the new number.

For example:

2845
would become
5482

How can you achieve that? I’ve had an idea where you could do a digit[i] array, null by default and receive as many values as the number has. For example 452 would give digit[3] : digit[1] would be 4, digit[2] would be 5, and digit[3] would be 2. But that sounds awfully complicated and printing it sounds like a pain in the butt, not to mention I couldn’t operate with the new digit. I need to check if the number read backwards is even.

Any ideas? I’ve been thinking on this one for quite a while, but I can’t figure out a proper solution. Also if it matters, I’m using eclipse IDE in the C language.

Answer 1

A simple solution would be:

/* only for x>0 */
int reverse(int x)
{
    int r = 0;
    while(x) {
        r = r*10 + (x%10);
        x = x/10;
    }

    return r;
}