It's a bit overly clever. I am a huge fan of Peter Norvig (and he was once my skip-level boss), but I'd call this code out in a code review for being obtuse.
Notice that the input, `nums`, is a set. So he's taking the intersection of two sets. One set always has one item, so the result will be a collection with either 0 or 1 items.
It could have also been written as:
first(x * (2020 - x)
for x in nums
if (2020 - x) in nums and x != (2020 - x))
But that has a lot of duplication, so it'd probably be best to just use an imperative approach here and do something like:
def day1_1(nums):
"Find 2 distinct numbers that sum to 2020, and return their product."
for x in nums:
y = 2020 - x
if x == y:
continue
if y in nums:
return x * y
Notice that the input, `nums`, is a set. So he's taking the intersection of two sets. One set always has one item, so the result will be a collection with either 0 or 1 items.
It could have also been written as:
But that has a lot of duplication, so it'd probably be best to just use an imperative approach here and do something like: