i think the increment could be i+=3 instead of i++
so u can simplify the ret calculation into
ret += 1f/i
xD

I could add an additional condition that is AND in the loop which is 0 > openBracesCtr.

Something like this:
for(auto i = index+1; i < str.size() && 0 > openBracesCtr; ++i)
{
//same as before, but break can now be removed.
}

Btw, in my opinion both solutions have similar performance. I guess it's for coders preference on which is more reable. Anyways, thanks for the suggestion. It's good to think a way in tweaking existing solutions. :)

i suggest adjusting the loop condition instead of using break inside the loop, unless it's a must :')

Most compilers will optimize the code so that size() isn't called every iteration. In theory, you are correct, though.

Suppose size_t i instead of int i would be more correct as well. Iterators probably could have a case here.

Im attemping in C#.

When i run sample test on test 1 it passes (case 1: empty | case 2: 3 pairs)

But when i attempt, it doesn't pass test 1(case 2) and my output array is missing the last pair :O

i tested it again with online complier and it gives correct array with 3 pairs :thonking: