The Nineteenth Byte

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Conor O'Brien

04:51

@lirtosiast I answered one of your bounties :)

5 hours later…

lirtosiast

09:59

@ConorO'Brien Nice, will start the bounty tomorrow

5 hours later…

bushdid911

15:10

i have an (i think) pretty solid idea for a challenge, my issue is that I don’t know how to provide test cases and diagrams on Desmos because I’m not sure how to efficiently solve it..

TRITICIMAGVS

@bushdid911 What's the idea?

bushdid911

Is there a character limit on messages in this chat?

Well, further consideration has led me to think that it may not be such a good idea. It would be a variant of this problem: codegolf.stackexchange.com/questions/179938/… with the specification that certain walls can be considered mirrored and can reflect light. I thought about just modifying it to make them all mirrored but google shows that polygonal rooms can be illuminated everywhere except a finite number of points (thus having zero area).

I thought about just modifying it to make them all mirrored but google shows that polygonal rooms can be illuminated everywhere except a finite number of points (thus having zero area). Since they’re not all mirrored I can probably figure out a solution (though not an efficient one) just by checking every side

TRITICIMAGVS

Ah I see. Yes this is a bit harder.

Also the character limit is higher if you do a multiline message.

4 hours later…

Erik the Outgolfer

18:57

feedback request

Anonymous

19:34

@EriktheOutgolfer The second sentence seems to have a word or two missing, but other than that, it's clear to me. I'd recommend adding some test cases in an easy-to-parse text format at the end.

Erik the Outgolfer

"a layers"? :P

Anonymous

Especially test cases with multiple solutions - I expect that to be the hard part for most answers

Erik the Outgolfer

yeah, that's probably the hard part (was thinking about it while writing it), especially if the pyramid doesn't have the topmost number already filled in (yes, there might be a unique solution for that too)

Anonymous

I think languages with linear algebra utilities will do the best, as the problem can easily be represented as a linear system

Erik the Outgolfer

obviously

Anonymous

20:00

For some reason, Sage can't solve the linear system produced by the first example...

Erik the Outgolfer

the "unique solution" one?

Anonymous

Yeah

Anonymous

6 linear equations with 7 positive unknowns yields underdetermined, but adding in a 7th equation (sum of any row equals sum of any other row) yields no solution

Erik the Outgolfer

maybe you didn't restrict it to the non-zero positive integers? because that's how you can infer a + b = 2 → a = b = 1

Anonymous

Oh true, I only specified positive

Erik the Outgolfer

20:06

also, the 7th equation you added isn't true

row a, b, c yields row a + b, b + c, and a + b + c ≠ a + b + b + c

Anonymous

Oh right

Anonymous

Well, with that removed, and with the positive integer assumption added, it still doesn't solve it >_<

Erik the Outgolfer

can you link to an online interpreter? maybe you have a typo over there :P

Anonymous

link

Anonymous

r1 should be 4, but it refuses to make that logical leap

Erik the Outgolfer

20:16

weeeeird...

Anonymous

20:32

now this is just silly

Anonymous

Highlight: nnn > 0, nnn is integer, [...] 0 < nnn, nnn < 2

Erik the Outgolfer

lol

clearly, Sage isn't perfect

Anonymous

So nnn is a positive integer between 0 and 2 exclusive... The technology just isn't there yet.

Erik the Outgolfer

having a hard time figuring out what nnn actually is... wait a few years for me please...

Anonymous

The worst part is, Sage uses Maxima for this, which is usually solid

New Sandboxed Posts

21:01

A: Sandbox for Proposed Challenges

Can this container hold this much liquid? code-golf geometry Challenge Synopsis As you most likely know, liquids have an indefinite shape and a definite volume. As such, they always take the shape of their container. They cannot, however, expand to fill their container. Your job today is to d...

Newly Featured Questions

21:56

Q: Help! My calculator broke! (Turn integer expression into calculator keystrokes)

Introduction Help! I accidentally dropped my TI-84 calculator out my window (don't ask how) and it broke. I have a math test tomorrow and the only calculator I can find is one with these buttons: 7 8 9 + 4 5 6 - 1 2 3 * 0 = / My math test is a review test on evaluating expressions. I need a...

Anush

22:12

here is a fun math puzzle

Consider $f(x) = 2018/(100 + e^x)$. How many integers are in the range of f?

Blue

Is anyone good with elasticsearch? I'm getting rather confused with it

Anush

22:30

ok here is a more algo type puzzle

. You are given a sorted array of n elements which has been circularly shifted. For
example, {35, 42, 5, 12, 23, 26} is a sorted array that has been circularly shifted by 2
positions.
Give an O(log n) time algorithm to find the largest element in a circularly shifted
array.

lirtosiast

22:42

@Anush Try it online!

@Anush isn't this just binary search?

Quintec

@lirtosiast It's like "quicksort-style" binary search

You find the "pivot" point of rotation and then split there

Finding the pivot with binary search

Don't be a x-triple dot

@Anush Mhm, $f(x)$ is maximum at $e^x\to 0$ (and it can get arbitrarily close to $0$ so $f(x)\le 20.18$), but as $e^x\to\infty$, $f(x)$ gets arbitrarily close to $0$ but never actually reaches $0$, so the answer should be $20$?

Doorknob

but if x can be complex then the answer is infinitely many

New Main Posts

23:26

Q: Arbitrary Interval Ruler

Make a program that takes a length and list of intervals and outputs a ruler of that length with longer ticks for each interval using the line drawing characters ┌ ┬ ┐ │ ╵ The first row of the output should begin with the tick for 0 with ┌ and end with a tick for the length with ┐, with a ┬ bei...