Re: find a number

Mark P:

There's also a cute algorithm for this problem which runs in linear
time, uses constant space, and performs no arithmetic computations on
the array elements.

In theory ;)
For example X==Y only seems to not do arithmetics ;)
X+Y or X-Y vs X==Y make no difference for real.

I hated going to weddings.
All the grandmas would poke me saying "You're next".
They stopped that when I started doing it to them at funerals.