The modern calendar is a trap for the young engineer’s mind. We deal with the calendar on a daily basis and until exposed to its insanity it’s rather common to think that calendar based computations are easy. That’s until you’ve tried to do it once. A very good read about how the current calendar came to be the way it is now is Erik’s Naggum The Long, Painful History of Time.
A recent interview question that I had to review was spelled like this:
Find missing int element into array 1..100
Of course at first read I got it wrong, you have only one integer to look for into the array. So while the obvious idea was to apply classic sorting techniques and minimize array traversal to handle complexity (time and space), it turns out there’s a much simpler way to do it if you remember your math lessons from younger. But is it that much simpler?