Why is this program a mistake?

Question

When i challenged the "extra terrestrial" practice i made the program like this:

https://code.sololearn.com/c88K0XyFp1x3/?ref=app

But when i run it the system tells my program is wrong although it gives output that as same as expected output. Can anyone tell me where i did wrong or is it a bug in the system?

Answer 1

I don't know about C
But I think this may cause an error, because in most programming languages indexing starts from 0.
So in the first iteration you are trying to get out of range value.
For example if the length is (5)
The last item's index would be 4 not 5.

Try this

int main() {
char a[100];
scanf("%s", a);
int x = strlen(a);
for (int i = 0; i < x; i++) {
printf("%c", a[x - i - 1]);
}
return 0;
}

Answer 2

Celvien Kurniawan notice that inside the loop, a[x-i] is past the end of the input string when i=0. The loop index should start with 1 instead of 0. The rest is good and will pass after that correction.

Answer 3

I see... Thank for the info. I'll try just like that.