int reverse(int n)
{
int temp,rem;
int reve =0;
int flag =1;
temp = n;
while(temp!=0)
{
rem = temp % 10;
reve = reve*10 +rem;
temp = temp/10;
}
if(reve==n)
{
flag = 0;
}
return(flag);
}

int prime(int n)
{
int i;
int flag =0;

for(i=2;i<=sqrt(n);i++)
{
if(n%i==0)
{
flag = 1;
}
}
return(flag);

}

my solution is fine but i am getting “TIME LIMIT ERROR” so if some one could help me in optimising this code .
it just check whether number is a prime and is a palindrome or not using two function http://www.codechef.com/problems/PRPALIN/ —> it’s a practice question

You have declared n as int but range of n is beyond int maybe because of that your are getting tle
try using long long int also change %d to %lld for long long int.
Your logic is correct

There are many places where your code can be optimized for speed. The most effective ones are in your prime checking function. You should add break statement if n is divisible. Also when asking for help, always format your code correctly or provide a link for better readability.

int prime(int n) {
int i,flag=0,lim=sqrt(n); //sqrt calculated only once, not every time
for(i=3;i<lim;i+=2){ // loop starts from 3 for speed up as we have already skipped even //numbers and increase by 2 in each step
if(n%i==0) {
flag=1;
break; // added break here
}
}
return(flag);
}

Other places need to be modified too for faster execution.

See your code accepted with a lot of speed up modifications by me here.

The worst case complexity of your solution is O(N*sqrtN).
For the given problem it becomes 10^9 iterations.
But in 1s (time limit for the problem) your processor( or codechef’s which is even slower) can perform about 10^6 iterations resulting in almost 1000s for the worst case.