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Wouldn't be that hard to implement. We just need a modulo (like I did) when
sending #next to wrap around...
Or even better: a "cyclic" iterator, something like #withWrapDo: ?
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Benoît St-Jean
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"A standpoint is an intellectual horizon of radius zero". (A. Einstein)
On Monday, December 3, 2018, 1:28:09 p.m. EST, phil--- via Pharo-users
<pharo-users@lists.pharo.org> wrote:
CyclicReadStream. Not in base Pharo.
I wish.
We have atWrap: but not the best.
Phil
On Mon, Dec 3, 2018 at 1:17 PM Richard O'Keefe <rao...@gmail.com> wrote:
"if I use do: this ends at the end of the array."True. But all that means is
that you have to keen on using #do:.
Processing an array repeatedly is as simple as [true] whileTrue: [ anArray
do: [:each | ...]]
I had intended to twist this into
[changes anySatisfy: [:change | ...]] whileFalse.
However, in this case your second alternative has much to recommend it.The
control flow is simple. There's no magic about it. It's anunusual setup, so
no need to get fancy.
seen := Set new. frequency := 0. found := false. i := changes size.
[found] whileFalse: [ i := i = changes size ifTrue: [1] ifFalse: [i+1].
frequency := frequency + (changes at: i). found := seen includes: frequency.
seen add: frequency].
I like this better than what I had.
If we _were_ to get fancy, then introducing a CyclicReadStreamclass and doing
seen := Set new. frequency := 0. found := false. stream :=
CyclicReadStream on: self changes. [found] whileFalse: [ frequency :=
frequency + stream next. found := seen includes: frequency. seen add:
frequency].wouldn't shrink the code much. Oddly enough, I've
encounteredproblems in previous Advent of Code exercises where
CyclicReadStreamwould have been handy. But just for this case? No.
On Tue, 4 Dec 2018 at 00:25, Roelof Wobben <r.wob...@home.nl> wrote:
hello Richard,
Thanks, I figured that out already.
What I do not get is how to read the array multiple times.
if I use do: this ends at the end of the array.
Or I must use something as this :
index := 0
if index > array length
index =: 1
else
index := index + 1
and then read the number with array at: index
Roelof
Op 3-12-2018 om 10:08 schreef Richard O'Keefe:
Roelof Wobben wrote "I have to reread the file till the adding causes the
same outcome as we had already" You have to process the *sequence of changes*
repeatedly; you DON't have to *reread the file*. Somebody already made this
point. Having read the changes into an array, you can iterate repeatedly over
that array.
to find the first repeated frequency given a sequence of changes make an
empty Set to hold the sums that have been seen so far.
set the frequency to 0. loop forever for each change in the
changes increment the frequency by the change. if the
frequency is in the set return the frequency
otherwise add the frequency to the set.
partTwo: aFileName Transcript print: (self firstRepeatedFrequency: (self
changesFrom: aFileName)); cr; flush.
On Mon, 3 Dec 2018 at 19:31, Roelof Wobben <r.wob...@home.nl> wrote:
Thanks,
For the second I have to take a good look.
I have to reread the file till the adding causes the same outcome as we had
already
so for example if we have the sequence :
+3, +3, +4, -2, -4
it has as outcome :
3 6 10 8 4
so no outcome is there a second time so we repeat the sequence
7 10
the 10 shows up a second time so there we have our answer.
Roelof
Op 3-12-2018 om 03:45 schreef Richard O'Keefe:
The key question is "what do you mean by improve"? I'd start by asking "what
are you doing that you will still have to do in part 2, and what won't you do?"
So looking at part 2, you will want to convert the lines to integers, and
input := Array streamContents: [:lines | 'input.txt' asFileReference
readStreamDo: [:in | [in atEnd] whileFalse: [lines nextPut: in nextLine
asInteger]]]. gives you a chunk of code you can use in both parts. So you
might want to have
Day1 changesFrom: aFileName ^Array streamContents: [:changes |
aFileName asFileReference readStreamDo: [:in | [in atEnd] whileFalse:
[changes nextPut: in nextLine asInteger]]] partOne: aFileName ^(self
changesFrom: aFileName) sum partTwo: aFileName ... The file name should
not be wired in because you want some test files.
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