Question

I’m writing a program that list the digits of integer input.

example:

Please enter an integer number: 5021
The digits are:
5
0
2
1

The program works fine except when it comes to numbers ending in 0 since I have reversed the number first using a while loop (while num>0)in order to print the numbers in the order shown above. I hope someone can point me in the right direction as I really can’t seem to think of another way just now 🙂

sorry couldn’t figure out how to add code without doing 4 spaces in front of each line (is there another(easier) way to add code?).

int main() {
  int userInt; /* integer input by user */
  int revInt;  /* reversed integer */


  printf("Please enter an integer number: ");
  scanf("%d", &userInt);

  /* reverse int */
  revInt = reverseInteger(userInt);

  /* print digits */
  printDigits(revInt);

  return 0;

}

int reverseInteger(int num) {
  long sum = 0;
  int remainder;

  while(num) {
    remainder = num%10;         /* get last digit of number */
    sum = sum*10 + remainder;   /* move digits by one place in sum and add remainder of number */
    num = num/10;               /* remove last digit of number */
  }

  return sum;
}

void printDigits(int num) {
  int remainder;

  printf("The digits are:\n");

  while(num) {
    remainder = num%10;         /* get last digit of number */
    printf("%d \n", remainder); /* print last digit */
    num = num/10;               /* remove last digit of number */
  }
}

Answer 1

The maximum number of digits in an int is small so you could safely use recursion in this case:

#include <stdio.h>
#include <stdlib.h>

void
print_digits(unsigned n) {
  div_t q = div(n, 10);
  if (q.quot > 0) print_digits(q.quot);
  printf("%d\n", q.rem);
}

int main() {
  print_digits(50210);
  return 0;
}

Output

5
0
2
1
0