Three glasses of whisky
The last one looks obvious - but it is a case of the brain seeing what it expects to happen - rather than what the instructions actually will do. Lay people have difficulty in understanding that you can't lie to a computer - being too precise can also be wrong if there is an unknown factor.
In the old days it was the sort of problem that you knew you just couldn't see for looking - it had to be obvious.
As a very occasional drinker I would look at such a problem while working through three glasses of whisky. The increasing intoxication meant my thinking became slower and slower - and eventually I had to reason very hard about each step in the code.
Usually I spotted it by the third glass - otherwise I went to sleep. If I was lucky the answer rose unbidden as I awoke the next day.
That only works if a small amount of alcohol has that effect on you - regular drinkers would have a higher threshold.
Biting the hand that feeds IT
