This is a great and clever solution. But is this performant for longer solutions compared to HashSets ? I am new to codewars. The tradeoffs between efficiency and one liner functions are interesting.

DUDE. CLEVER.

Began to learn C# like, a few months ago.
Wrote literally a massive thing after one hour just to see this

I feel dumb, but holy geez, that was very, very interesting to see! Congrats, fella.

cool

Or the other way round?

So basically if a character repeats in a string it return true and if it doesnt it returns false?

Now I am curios if there is an even shorter way to solve this....

@pescadomuerto: when it comes to time complexities, most of the time comparing the number of passes is meaningless. You're currently sort of saying that 3*n != n*3. That's why the asymptotic behavior is ignoring the constant factors.