Your comparison function does not account for integer over/under flow ;-) that's the point of these fixed tests

They're not, the description was awkwardly worded. If the input cannot be arranged into a square, it is invalid and you have to return "No"

You should provide an example...

Here's one:

Testing for [1, 0, 1]
It should work for random inputs too: 'Yes' should equal 'No'

Same for [1, 1]

If it's a problem with your algo, please mark as a question, not an issue. EmperorMigx is correct, you have to allocate memory and mind your type.

The numbers of letters from 'sabbatical' that are present in string s.

You're not doing that. Read the description again.

Hi, there's no issue here. You're adding up all 5 letters in the input 'cCdvi' where cCdvi > 5 + 10 + 9 = 24, meanwhile 'd' and 'v' are not in the word 'sabbatical', so they should not be counted.

What language you're using? if C then you should mind the return type.
In this case the return type is size_t
Use calloc bro this was my error too. I'm using C.

BTW if you see this, would you not mind if you already finished g964 Kata's the:
Rectangle into Squares and Backwards Read Primes

I believe I know how to solve it but I don't know how to return the value. I've rewritten it without using typedef struct and I manage to have correct answers. But in the format typedef struct in those katas I'm getting error: Caught unexpected signal: 6

unsigned long which is 32 bit in C

It's at least 32 bits.

Input values are up to 64 bits.

Which implies that unsigned long has this size on this platform.
I've just checked, everything works. Check your solution.