## Issue

I’m trying to create a recursive function to reverse digits of a number in C. This is what I’ve written. It works fine when used one time but when used multiple times it keeps piling the numbers together. I think the problem can be sorted if the sum is initialized to zero each time the function is called but I’m unable to do it. I’ve tried declaring sum=0 as a global variable but the result was the same.

Input-

12

23

34

45

Output

21

2132

213243

21324354

```
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
int digit_reverse(int N)
{
int rem;
static int sum=0;
if(N>0)
{
rem=N%10;
sum=sum*10+rem;
digit_reverse(N/10);
}
else
return 0;
return sum;
}
int main()
{
int a[25],i;
for(i=0;i<4;i++)
{
scanf("%d", &a[i]);
}
printf("Output\n");
for(i=0;i<4;i++)
{
printf("%d\n",digit_reverse(a[i]));
}
}
```

## Solution

Maybe you can write your function without using static variables:

```
void _digit_reverse(int N, int *sum)
{
int rem;
if (N > 0)
{
rem = N % 10;
*sum = *sum * 10 + rem;
_digit_reverse(N / 10, sum);
}
}
int digit_reverse(int N)
{
int sum = 0;
_digit_reverse(N, &sum);
return sum;
}
```

Or take the sum outside:

```
int sum = 0;
int digit_reverse(int N)
{
int rem;
if (N > 0)
{
rem = N % 10;
sum = sum * 10 + rem;
digit_reverse(N / 10);
}
else
return 0;
return sum;
}
int main()
{
int a[25], i;
for (i = 0; i < 4; i++)
{
scanf("%d", &a[i]);
}
printf("Output\n");
for (i = 0; i < 4; i++)
{
sum = 0;
printf("%d\n", digit_reverse(a[i]));
}
}
```

I believe that the static variable gets initialized only once. This is the problem with your approach.

Answered By – Shahriar

Answer Checked By – Jay B. (BugsFixing Admin)