Thread: Integers Decomposition

A couple of options:

1. Read the "integer" in as a string, check each character with isdigit(), and then reverse the string. This will allow "integers" of arbitrary length.
2. Read it into an integer variable, print it to a string with sprintf(), then reverse the string. This will limit you to the actual range of the integer type that you choose.

Originally Posted by Elkvis

A couple of options:

1. Read the "integer" in as a string, check each character with isdigit(), and then reverse the string. This will allow "integers" of arbitrary length.
2. Read it into an integer variable, print it to a string with sprintf(), then reverse the string. This will limit you to the actual range of the integer type that you choose.

There's at least a 3rd option:

Code:

#include <stdio.h>

void print_digits(int x)
{
  if (x > 0)
  {
    putc((x % 10) + '0', stdout);
    print_digits(x / 10);
  }
}

int main(void)
{
  int x = 1234;
  print_digits(x);
  return 0;
}

If you choose not to use recursion, because there is a problem here if the integer (at the first call of the function) is 0--since it won't output anything, you can still change this over to a while loop and avoid having to create a special case for 0. The other issue is with negatives... Not sure if that's an issue here, but you could take the absolute value of the number still, and set a flag if the number is x < 0.

The only issue here is with datatype limitations, that wouldn't exist if you were to just avoid integers and deal with strings.

Read in an integer
As stated above, use the modulus function to get the *last* digit
A simple WHILE loop will suffice, recursion overkill