Fill in the lakes

Question

Given the topography of land in ASCII picture format, figure out where lakes would go and fill them in. Assume an infinite amount of rain.

example

input

         #               
         ##              
      # ####             
#    #########           
##  ###########          
## #############   ####  
## ##############  ##### 
################# #######
#########################
#########################

output

         #               
         ##              
      #@####             
#@@@@#########           
##@@###########          
##@#############@@@####  
##@##############@@##### 
#################@#######
#########################
#########################

The input will contain only spaces and # marks. Each line will be the same length. The output should be the identical # pattern with spaces where water would accumulate filled in with @ marks.

The bottom input row will always be all # marks. There will be no holes or overhangs in the land. Shortest code wins.

This seems a bit easy. I think we should also have to display the number of lake units @ that were filled in. — mellamokb, Commented May 12, 2011 at 20:53
@mellamokb: This would be roughly a ([char[]]"$a"-eq'@').Count here. Not that much too add. Agreed on this being a little too easy, though. Doesn't fall into the realm of what I'd downvote, though. — Joey, Commented May 12, 2011 at 20:55
Related on Stack Overflow: Code Golf: Running Water. One of LiraNuna's better one, I thought. — dmckee --- ex-moderator kitten, Commented May 12, 2011 at 21:41
So do we also have to handle underground caverns, which may have air above the water level like the Running Water puzzle? That makes things a little more challenging and I think should definitely be an example use case. — mellamokb, Commented May 12, 2011 at 21:45

asoundmove · Accepted Answer · 2011-05-20 04:38:22Z

9

sed -r, 27 24 (27 with `-r`)

24 (27):

:;s/(#|@) ( *#)/\1@\2/;t

~~27 (30):~~

~~:e;s/([#@]) ( *#)/\1@\2/;te~~

Competes with the better of the two perl solutions

edited May 20, 2011 at 4:38

answered May 13, 2011 at 4:29

asoundmove

3582 silver badges6 bronze badges

\$\begingroup\$ #|@ would be one char shorter \$\endgroup\$
– YOU
Commented May 13, 2011 at 6:34
2

\$\begingroup\$ You should add 3 to the count for the -r flag. You can cut off two from removing the es, and another from S.Mark's suggestion to get back to 27 though. \$\endgroup\$
– Nabb
Commented May 13, 2011 at 7:25
\$\begingroup\$ @Nabb thanks, discovered something with the empty label \$\endgroup\$
– asoundmove
Commented May 13, 2011 at 12:36
\$\begingroup\$ I tried sed before, but failed \$\endgroup\$
– Ming-Tang
Commented May 13, 2011 at 17:45

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Joey · Accepted Answer · 2011-05-13 07:24:51Z

8

Perl, 25

s/# +#/$_=$&;y| |@|;$_/ge

edited May 13, 2011 at 7:24

Joey

13.2k2 gold badges43 silver badges73 bronze badges

answered May 13, 2011 at 2:29

Ming-Tang

6,0373 gold badges25 silver badges45 bronze badges

\$\begingroup\$ I added a character count. Please look whether it's actually correct, as it might need to include some interpreter flags (-p maybe?). \$\endgroup\$
– Joey
Commented May 13, 2011 at 7:25
\$\begingroup\$ i dont know perl language, but i can feel its power :) \$\endgroup\$
– Ant's
Commented May 13, 2011 at 13:33
\$\begingroup\$ Actually it needs ` -pe` to function on my box, so that should be an additional 4 chars. Or does the e not count and thus only 3 additional chars required? \$\endgroup\$
– asoundmove
Commented May 13, 2011 at 23:24
\$\begingroup\$ Don't need the e, like I mentioned elsewhere, for the same reasons. :) \$\endgroup\$
– Robert P
Commented May 26, 2011 at 17:55
\$\begingroup\$ You can save a couple of bytes on this approach by inlining the change to $& without assigning to $_: s/# +#/$&=~y! !@!r/ge \$\endgroup\$
– Dom Hastings
Commented Jul 21, 2022 at 11:57

| Show 1 more comment

yibe · Accepted Answer · 2011-05-13 11:16:38Z

6

Perl (>= v5.9.5), 24 chars

Run with perl -p:

1while s/#.*\K (?=\S)/@/

This requires Perl 5.9.5 or later to use the special escape \K.

answered May 13, 2011 at 11:16

yibe

1611 gold badge1 silver badge3 bronze badges

1

\$\begingroup\$ Except that if Nabb is correct, you need to count ` -p` as 3 chars, bringing your total to 27. And it actually requires ` -pe. I don't know the full rules about flags, so not sure the e` counts. \$\endgroup\$
– asoundmove
Commented May 13, 2011 at 23:27
\$\begingroup\$ Wouldn't actually need the e, if you simply hit enter and type it in afterwards, or put the code in a file and run it. So -e isn't really needed. :) \$\endgroup\$
– Robert P
Commented May 26, 2011 at 17:52

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Community · Accepted Answer · 2020-06-17 09:04:33Z

3

Windows PowerShell, 36 74 138

$input-replace'(?<!^ *) (?! *$)','@'

edited Jun 17, 2020 at 9:04

CommunityBot

1

answered May 12, 2011 at 20:49

Joey

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Erik the Outgolfer · Accepted Answer · 2018-07-01 13:07:31Z

3

Retina, 10 bytes

Retina is (much) newer than this challenge. But this solution is too neat not to post it:

T` `@`#.*#

Try it online.

This is simply a transliteration stage which replaces spaces with @, but the operation is restricted to matches of #.*#, i.e. characters which are surrounded by land on both sides.

edited Jul 1, 2018 at 13:07

Erik the Outgolfer

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answered Jan 12, 2016 at 10:54

Martin Ender

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Ventero · Accepted Answer · 2011-05-20 08:07:46Z

2

Ruby 1.8, 30 characters

#!ruby -p
gsub(/# +#/){$&.tr" ","@"}

If anyone has an idea why this doesn't work in Ruby 1.9 (tested with 1.9.2p0 and 1.9.2p204), even though the documentation says it should work, let me know!

edited May 20, 2011 at 8:07

answered May 12, 2011 at 21:09

Ventero

10.1k3 gold badges24 silver badges55 bronze badges

\$\begingroup\$ That's really weird, adding in $_=$_. to the start of the second line makes it work in 1.9.2 so it's something to do with Kernel.gsub. Rubinius also fails without explicitly adding $_. \$\endgroup\$
– Nemo157
Commented May 13, 2011 at 6:51
\$\begingroup\$ According to 1.9.1 NEWS log, Kernel#getc, #gsub, #sub are deprecated. \$\endgroup\$
– YOU
Commented May 13, 2011 at 7:25
1

\$\begingroup\$ I think you can count this as 30 (27 + 3 for needing the -p flag). The hash-bash and name of the interpreter doesn't count. \$\endgroup\$
– Caleb
Commented May 18, 2011 at 10:55

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Community · Accepted Answer · 2020-06-17 09:04:33Z

1

Python, 95 92 bytes

for s in S.split('\n'):b=s.find('#');e=s.rfind('#');print s[:b]+s[b:e].replace(' ','@')+s[e:]

edited Jun 17, 2020 at 9:04

CommunityBot

1

answered May 25, 2011 at 18:41

0b1t

912 bronze badges

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DLosc · Accepted Answer · 2018-09-25 04:48:53Z

1

Pip, 15 bytes

aR:`#.*#`_TRs'@

Takes input as a multiline string via command-line argument: Try it online! (Alternately, specify the -rn flags and change the first a to g, and you can give input via stdin: Try it online!)

Same idea as the Retina answer: replace every match of the regex #.*# with the result of transliterating space to @ in the match. Pip can't match Retina's terseness for a pure regex problem--but it's not everyday that you can tie with Jelly, after all.

edited Sep 25, 2018 at 4:48

answered Sep 25, 2018 at 4:42

DLosc

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Community · Accepted Answer · 2020-06-17 09:04:33Z

05AB1E, 17 16 bytes

|εγć?D¨ð'@:sθJJ,

Try it online.

Explanation:

|            # Take all input-lines as list
 ε           # For each line:
  γ          #  Split the line into chunks of consecutive equal characters
             #   i.e. " ##   # " → [' ','##','   ','#',' ']
   ć         #  Split into head and the rest of the list
             #   i.e. [' ','##','   ','#',' '] → ['##','   ','#',' '] and ' '
    ?        #  Print this head
   D         #  Duplicate the rest of the list
    ¨        #  Remove the last element
             #   i.e. ['##','   ','#',' '] → ['##','   ','#']
     ð'@:    #  Replace every space with a "@"
             #   i.e. ['##','   ','#'] → ['##','@@@','#']
     sθ      #  Swap so the duplicated list is at the top, and take the last item as is
             #   i.e. ['##','   ','#',' '] → ' '
         JJ  #  Join the lists and individual items in the list together to a single string
             #   i.e. ['##','@@@','#'] and ' ' → "##@@@# "
           , #  Print with trailing new-line

naffetS · Accepted Answer · 2022-06-04 02:06:58Z

Vyxal, 20 bytes

□⟑Ġvṅḣ$₴:Ṫ\@Ḟ$¤ptJṅ,

Try it Online!

How?

□⟑Ġvṅḣ$₴:Ṫ\@Ḟ$¤ptJṅ,
□                    # All inputs wrapped in a list
 ⟑                   # Open an apply lambda, apply for each:
  Ġvṅ                # Group consecutive identical characters
     ḣ               # Head extract, push a[0], a[1:]
      $              # Swap
       ₴             # Print without a trailing newline
        :Ṫ           # Duplicate and remove the last item
          \@Ḟ        # Replace all spaces with "@"
             $       # Swap
              ¤p     # Prepend an empty string for the case that the list is empty
                t    # Last item
                 J   # Join top two things on the stack together
                  ṅ  # Join by nothing
                   , # Print with trailing newline

Eran W · Accepted Answer · 2022-07-22 17:20:17Z

1

Javascript (ES6), 44 bytes

x=>x.replace(/# +#/g,s=>s.replace(/ /g,"@"))

edited Jul 22, 2022 at 17:20

answered Jul 21, 2022 at 8:30

Eran W

1811 silver badge5 bronze badges

1

\$\begingroup\$ Nice answer :) You can replace (hah!) replaceAll(" ", ... with replace(/ /g,... (removing the space) to save another three bytes too! \$\endgroup\$
– Dom Hastings
Commented Jul 21, 2022 at 13:46

Add a comment |

BobTheAwesome · Accepted Answer · 2015-03-07 00:01:05Z

0

Javascript, 107 bytes

var f=function(x){return x.replace(/# +#/g, function(x){return "#"+new Array(x.length-1).join("@")+"#";})};

Ungolfed:

var f = function(x) {
    return x.replace(/# +#/g, function(x){
        return "#" + new Array(x.length - 1).join("@") + "#";
    })
};

edited Mar 7, 2015 at 0:01

answered Mar 6, 2015 at 1:43

BobTheAwesome

5194 silver badges9 bronze badges

\$\begingroup\$ I recommend that you (1) post a normally formatted version of your answer so it is easier to read and follow along and (2) look into to ES6... it could save you a lot of characters with your functions. \$\endgroup\$
– SirPython
Commented Mar 6, 2015 at 23:26
\$\begingroup\$ I'll post a normal version, but I'm not a ES6-type person. \$\endgroup\$
– BobTheAwesome
Commented Mar 6, 2015 at 23:58
\$\begingroup\$ @BobTheAwesome Why did you just suggest this edit? \$\endgroup\$
– Tim
Commented May 17, 2015 at 20:02
\$\begingroup\$ Oh goodness, I was attempting to fix the test-case error but I have this extension enabled in chrome, if you know xkcd. Sorry about that. \$\endgroup\$
– BobTheAwesome
Commented May 18, 2015 at 0:07
\$\begingroup\$ Besides the ES6 stuff: you don't need the space after the comma, you don't need the space after the second return, and you can remove the two semicolons, and it can just be function f(x)... or f=function(x)... \$\endgroup\$
– Adalynn
Commented Jul 1, 2018 at 15:37

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Community · Accepted Answer · 2020-06-17 09:04:33Z

0

Python, 108 106 92 bytes

import re
n=1
while n: S,n=re.subn('# +#',lambda m:'#'+'@'*len(m.group(0)[2:])+'#',S)
print S

edited Jun 17, 2020 at 9:04

CommunityBot

1

answered May 25, 2011 at 21:44

0b1t

912 bronze badges

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Erik the Outgolfer · Accepted Answer · 2018-07-01 14:58:40Z

0

Jelly, 15 bytes

Ỵ”@ẹ”#ṂrṀḟƲ$¦€Y

Try it online!

answered Jul 1, 2018 at 14:58

Erik the Outgolfer

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Razetime · Accepted Answer · 2021-01-22 17:37:56Z

0

APL (Dyalog Unicode), 28 bytes

'# +#'⎕R{'@'@(' '∘=)⍵.Match}

Try it online!

answered Jan 22, 2021 at 17:37

Razetime

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Stack Exchange Network

Fill in the lakes

example

15 Answers 15

sed -r, 27 24 (27 with `-r`)

Perl, 25

Perl (>= v5.9.5), 24 chars

Windows PowerShell, 36 74 138

Retina, 10 bytes

Ruby 1.8, 30 characters

Python, 95 92 bytes

Pip, 15 bytes

05AB1E, 17 16 bytes

Vyxal, 20 bytes

How?

Javascript (ES6), 44 bytes

Javascript, 107 bytes

Python, 108 106 92 bytes

Jelly, 15 bytes

APL (Dyalog Unicode), 28 bytes

Your Answer

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code-golf
ascii-art
or ask your own question.

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Fill in the lakes

example

15 Answers 15

sed -r, 27 24 (27 with -r)

Perl, 25

Perl (>= v5.9.5), 24 chars

Windows PowerShell, 36 74 138

Retina, 10 bytes

Ruby 1.8, 30 characters

Python, 95 92 bytes

Pip, 15 bytes

05AB1E, 17 16 bytes

Vyxal, 20 bytes

How?

Javascript (ES6), 44 bytes

Javascript, 107 bytes

Python, 108 106 92 bytes

Jelly, 15 bytes

APL (Dyalog Unicode), 28 bytes

Your Answer

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sed -r, 27 24 (27 with `-r`)

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