SPOJ: PALIN - The Next Palindrome: wrong output - c

Question

Here is the code for "The Next Palindrome" which I wrote in C:
#include<stdio.h>
int main(void)
{
int check(int); //function declaration
int t,i,k[1000],flag,n;
scanf("%d",&t); //test cases
for(i=0; i<t; i++)
scanf("%d",&k[i]); //numbers
for(i=0; i<t; i++)
{
if(k[i]<=9999999) //Number should be of 1000000 digits
{
k[i]++;
while(1)
{
flag=check(k[i]); //palindrome check
if(flag==1)
{
printf("%d\n",k[i]); //prints if it is palindrome and breaks
break;
}
else
k[i]++; //go to the next number
}
}
}
return 0;
}
int check(int n)
{
int rn=0;
int temp=n;
while(n!=0)
{
rn=rn*10+n%10; //reversing
n=n/10;
}
if(rn==temp) //number is palindrome
return 1;
else //number is not a palindrome
return 0;
}
It is a beginner level problem from SPOJ.
I tried to run this code on Codeblocks and it ran fluently.
In SPOJ, why is it showing wrong output?

Answer 1

In SPOJ, why is it showing wrong output?
This is nice solution and it works for small inputs, however it will not pass SPOJ for several reasons.
The requirement is:
A positive integer is called a palindrome if its representation in the
decimal system is the same when read from left to right and from right
to left. For a given positive integer K of not more than 1000000
digits, write the value of the smallest palindrome larger than K to
output. Numbers are always displayed without leading zeros.
Input:
The first line contains integer t, the number of test cases.
Integers K are given in the next t lines.
So which requirements are broken in your program?
1) Your assumption is that only 1000 numbers will be given for processing since
you declared
k[1000]
wrong, the number of lines is given in first line. It could be much more than 1000. You have to dynamically assign the storage for the numbers.
2)
The line
if(k[i]<=9999999)
assumes that input is less than 9999999
- wrong, the requirement says positive integer K of not more than 1000000 digits which imply that much larger numbers e.g. 199999991 also have to be accepted.
3) The statement
For a given positive integer K of not more than 1000000 digits
as well as warning
Warning: large Input/Output data, be careful with certain languages
leads us to conclusion that really big numbers should be expected!
The int type is not a proper vehicle for storing such big numbers. The int will fail to hold the value if the number is bigger than INT_MAX [phone]. (Check C Library <limits.h>)
So, how to pass SPOJ challange?
Hint:
One of the possible solutions - operate on strings.