nicely done :)

No, string literals are not allocated on the stack.

How is this respecting the "The returned string should be statically allocated and it won't be freed" requirement? The "true" and "false" here are declared on the stack on the function call, not on the heap and it will BE considered freed and eventually overwritten by some other process using the heap later down the road.
Although it "works" on the surface, returning strings like that will evenatually crash your programs.

I don't agree with you

How would you simplify it?

i think it's uneed complicated

can someone explain this

Random test on C is not correct.

From random test output:
s: zdedhsvygbbsbpwodhpkzxnzoyjkfrrjgctpvsydqztlxsqsdjlihlzqweqtxqnnfcobngdkwqioghilkqpyslhozhiaiedyfrlpansybvwpivcqvxayhxkikngrhyvohghliaugiptqqruhxaruywajwdsasoojfzjfxonrtnagikbobqfyzpkssngsrlunvye
expected 'odctkwhzqhasft' (len = 14)
but got 'awospirxjguscuznae' (len = 18)

In random test answer is not longest string.
Please check it.

I solved this kata, but random tests are still not correct.
Random tests was passed by accident.
Error in random tests not fixed.

C:
random test may be not correct.
My C code converted to C# code with no changes in logic (changes only for array and memory allocation) worked.
I tested two versions of very simple C code.

Hi!

Test on C is not correct.
I print your random test string and dictionary. My code find longest string, I checked it in the manual.
In random test answer is not longest string.

Please check it. Thanks.