5 ms·
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. N
by sgk284 6y ago
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
- philshem 6y agowhen I saw the first() function, I thought it was some default python that was new to me. But he defines it above in his commonly used functions: def first(iterable, default=None) -> object: "Return first item in iterable, or default." return next(iter(iterable), default)
- notretarded 6y agoabstruse Completely agree, your solution is more clear.
- Gupie 6y agoThe "x == y" test looks like a bug to me, unless duplicate entries are not allowed. For example [1010,1010,1721,979,366,299,675,1456] should return 1010 * 1010, not 1721 * 299.
- deleted 6y ago[deleted]
- jstanley 6y agoGiven that the comment says "Find 2 distinct numbers that sum to 2020", I expect duplicate entries are not allowed.
- Gupie 6y agoYes, but I cannot find the same in the problem definition: "they need you to find the two entries that sum to 2020 and then multiply those two numbers together" https://adventofcode.com/2020/day/1 https://adventofcode.com/2020/day/1
- dubya 6y agoThere are frequently non-stated properties of the input in Advent of Code that simplify the problem a bit.
- tuvistavie 6y agoI am not sure I would advocate for this but, from Python 3.8, this is an instance where assignment expressions could allow the first code without duplication. first(x * y for x in nums if (y := 2020 - x) in nums and x != y)
- norvig 6y agoI agree, tuvistavie! But my default machine has 3.7 installed, and I didn't want to get too far ahead of readers. Sometime next year I'll go to 3.8, and look forward to using ":="