Unless the question has been edited recently, it did. There are multiple lines in the second example input that show the overlap:

> eightwothree

> 4nineeightseven2

> zoneight234

I test my AoC solutions incrementally by printing output, so I found that I was failing to produce the correct list of numbers in a line right away. I suppose if you're taking a faster approach and just trying to extract the first and last numbers that it's easier to miss. It's always a good idea to look at the example input, though.

Those examples contain overlap, but not in the first or last digit that is given as the solution. So from the instructions you can't tell that the intermediate list of numbers should be 8, 2, 3, you only know that the final answer is 83.

So are you saying that overlapped characters can be used for both numbers?

Meaning:

- eightwothree -> 823 (answer 83)

- 4nineeightseven2 -> 49872 (answer 42)

- zoneight234 -> z18234 (answer 14)

I interpreted the instructions as saying to take the first match from the left and not count the overlaps.

Unfortunately this gives the same answer as the overlap interpretation on the examples given in the problem statement: all the overlaps occurred in the middle where they didn't matter.

If they had shown

oneight -> answer: 18

then I would have understood the spec.

It could have been more clear. The wording from the problem is "the last digit on each line". To me, that pretty clearly implies "the rightmost substring containing a digit", but I guess I can see how someone could question that interpretation.

I think it strongly implies a direction with the example in part 1 where there's only a single digit resulting in "77" rather than "7".

Right, but we read the word "eight" from left to right -- to me it is non-obvious that "eightwo" should be counted as two digits when (a) there aren't enough characters to actually make both digits and (b) there wasn't a single example showing this overlap expanded

But I suppose can see the other side as well: the wording makes it sound like any spellings of those digits _counts_ as a digit rather than should be _replaced_ by a digit.

However I think the ambiguity here made the puzzle more difficult in a non-fun way.

Yes, same. I keep seeing people say this on discord and reddit, but that edge case was shown twice in the example.

It shows an overlap, but it doesn't indicate how one should parse it.

It showed "eightwothree" to be 83. Or is that not what you are talking about?

If it had shown "eightwo" as the last part of a string, then people with overlap would fail the example because they'd be finding "eight" where "two" would be correct. Having it at the beginning means it was overlooked, at least for me.

Though, I have no problem with the "spec". This a code puzzle game, so figuring that out was part of the fun, in my opinion

None of those it matters that much though. The test case of `eightwo` would be the most critical and unintutive.

I'm not certain, but I _feel_ like those are new values. There's a very real chance (majority chance) I'm wrong and oblivious though.

> No hate on AOC though, I really respect all the hard work that goes into it.

100% with you on this. Last year was the first year I'd had time to complete it, and I always love the challenge.

Yeah I was sort of lucky that my edge case was on the last line, still took a full hour of wondering why my solution was wrong though.

I find some problems of AoC are sometimes on the thin line between "it's interesting and I might learn something new" vs "wasting my time with under-specified or ambiguous problem specs".. Part 2 of Day 1 lies dangerously in the latter, for me.

What was this edge case you encountered? My code worked...after I finally read the problem closely enough.

For me it was a lack of specific instructions on how to handle overlaps. The edge case that frustrated me for a while was "oneight" at the end of a line. My initial code made it look like this "1ight", when it should have been "18".

When searching for the last number in the line I just reversed the line and scanned through it looking for the reversed strings for the number:

one -> eno

two -> owt

three -> eerht

etc

It makes the entire solution extremely simple, though a little verbose.

Yeah I was a little confused about all the people saying they've already given up on day 1. Seems like everyone's just really overcomplicating this. Why is everyone jumping to "replace the word strings with the digits" instead of just doing exactly what the problem says and... finding the first and last occurrence?

1. Build a list of values with corresponding string matches: [ 0 => ['zero', '0'], 1 => ['one', '1'], ...]

2. Loop through that and find the index of each within the input string, maintaining the lowest seen index + associated value.

3. When done, return value.

To find the last occurrence... just reverse the input string and all the search strings.

I'm not even sure it's all that verbose. If you exclude the part where I hardcoded an array of ten digits, it was... 11 lines of code, a third of which are closing braces. I'm sure I could cut it in half if I used some builtins for mapping/reducing/etc.

> I'm not even sure it's all that verbose

Mine is. But that's because I don't bother DRYing it and making it more clever (yanking and pasting is faster than thinking)

Same here. I'm using regex and I was wondering how to make it go backwards. After a moment of thought, that seems silly, so I just reversed the string and the regex and do the scan.