Reversing a number with 0s in the last position in C - c

Question

I've got this simple code for reversing integers. But I need to reverse numbers with leadings 0s now for another project. For example, this program is able to convert 32 to 23, but it converts 3200 to 23 as well. I need the 0s to stay in the leading place. However I've seen the binary operations on a bit level that can do this job, I'm looking for a way(if any) to do it without using bitwise operations and keeping it simple.
#include <stdio.h>
int main()
{
int a, mod = 0, reverse = 0;
printf("Enter a number:");
scanf_s("%d", &a);
while(a!=0)
{
mod=a%10;
reverse = reverse * 10 + mod;
a=a/10;
}
printf("%d", reverse);
return 0;
}

Answer 1

Record the scan offset with "%n" when reading the integer.
Use the text width of the number to control the reversal and printing.
int main() {
int a, mod = 0, reverse = 0;
printf("Enter a number:");
int n1, n2;
scanf(" %n%d%n", &n1, &a, &n2);
int width = n2 - n1;
while (width-- > 0) {
mod = a % 10;
reverse = reverse * 10 + mod;
a = a / 10;
}
printf("%0*d", n2-n1, reverse);
return 0;
}
Example
Enter a number:00123
32100
Enter a number:12300
00321
Other considerations not handled.
sign character '+' or '-'.
Input outside int range
Reversed number outside int range.
Non-numeric input.

Answer 2

I think you should approach this problem as if the input where a string.
#include <stdio.h>
#include <string.h>
#define MAX 15
void xor_swap(char *a, char *b) {
if(a != b) {
*a ^= *b;
*b ^= *a;
*a ^= *b;
}
}
int main(int argc, char **argv) {
char buffer[MAX];
size_t length;
printf("Enter a number: ");
fgets(buffer, MAX, stdin);
//fgets also includes the newline chracter so we get rid of that.
length = strlen(buffer);
buffer[length - 1] = '\0';
length--;
for(int i = 0; i < length / 2; i++) {
xor_swap(&buffer[i], &buffer[length - i - 1]);
}
printf("buffer: %s\n", buffer);
}

Answer 3

I would like to take slightly different approach.
I would request somebody to do the code indentation for me as I am using cell phone to answer.
# define SIZE 10
int main ()
{
int num= 3200;
// keep one array of characters to store the reversed digits.
char reversed_digit[SIZE];
int i= 0, temp;
if (num == 0)
reversed_digit[i] = (char) num;
else.
{
while (num > 0)
{
temp= num % 10;
num= num / 10 ;
reversed_digit[i++]= (char) temp;
}
reversed_digit[i]= '\0';
}
printf("The reversed digit is: %s ", reversed_digit);
return 0;
}