Question

I’m trying to reverse the numbers input by user (i.e. numbers input by user are stored in an array as long as he inputs a positive number ).
However, when I input
123 4569 752 896 -1
the output is
321 9653 257 698
As you can see the second number is not 9654. I couldn’t fix it.

#include <stdio.h>
#include <math.h>

// finding the number of digits
int bsm(int a){
   int i=0;

   while(a!=0){
      i++;
      a=a/10; 
   }

   return i; 
}

// reversing the number
int rev(int m,int a){
   int s=0,sum=0;

   while(a!=0){
      s=a%10;
      sum+=s*pow(10,m)/10; 
      m--;
      a=a/10; 
   }

   return sum;
} 

int main()
{
   int i=0,k,a[10],p,r;
   scanf("%d",&a[i]);

   while(a[i]>0){
      i++;
      scanf("%d",&a[i]);
   }

   for(k=0;k<i;k++){
      p=bsm(a[k]);
      r=rev(p,a[k]);
      printf("\n%d ",r);
   }

   return 0;
}

Answer 1

Since this looks like homework, I’ll limit my answer to two hints.

1. When you use pow(), it returns a floating-point number, and floating-point numbers are inexact. Rewrite your program using only integer maths or strings.

2. Think about how you wish to handle numbers that end in zeroes; for example, what should be the reverse of 2000?