I’m watching Brooklyn 99 rn and got to the episode with the 12 Islanders riddle (S2E18 for anyone curious) and I thinkI managed to figure it out (I can’t remember if they tell you in the episode so this is just me) so you can only use see saw 3 times
So what you do is you weigh 6 islanders at a time, 3 on each side, do this twice, since only 1 islander is an odd weight, you’ll find the group he’s in by at least the second weigh in, then you take any 2 from that group of 3 and he’ll either be on the scale or the only one not on the scale depending on if the see saw is balanced or not
I might be an amazing human/genius