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#8: Post edited by

jhnc‭ · 2026-06-07T02:32:23Z (3 months ago)
accessing @- for offset of match start saves 2 bytes; improve comments

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~~# [Perl 5], 98 bytes~~
Read stdin. Exits 1 if net, 0 if not.
```bash
~~perl -00ae'@l=@r=map{++$c[(pos)-1]while/#/g;y/#//||()}@F;@r>@c?@r:@l=@c;exit!grep$r[$_]>@l-2,0,-1'~~
```
When oriented with longer side vertical as shown in the challenge:
* nets have height 4 or 5
* nets never start or end with a "long" column (2+ for height 3; 3+ for height 4; 4+ for height 5) but non-nets always do
* for non-nets of height 3 the squares may not be connected when the other orientation is chosen
This simplifies to:
* non-nets have an start or end column containing more than height-2 squares
```
printf "%s\n" '...#..' '####..' '...#..' '......' '......' '......' |
# -00 slurps records in paragraph mode
# -a loops over records, with lines stored in @F
perl -00ae'
# compute array of non-zero counts of rows
# initialise length direction to horizontal
~~# because "row" counts will be compared to length,~~
# switch either @r or @l to other direction below
@l = @r = map {
# part-compute array of non-zero counts of columns
~~++$c[(pos)-1] while /#/g;~~
y/#// || ()
} @F;
# set length to vertical if appropriate
# or use columns for counts
@r>@c ? @r : @l
= @c;
# test if start or end count is out of range
# exit with the negation to save a character
exit ! grep $r[$_]>@l-2, 0,-1
'
echo $?
```
~~[Try it online!][TIO-mptr86vk]~~
[Perl 5]: https://www.perl.org/
[TIO-mptr86vk]: https://tio.run/##pVldT9tAEHzPr3AzQSQiuYRKfSEC8tQ/AQjRyIVIaRLZQS0C/npTEvLhO@/tzqU8YIzO573d2Z3Z9SIvpt9WyJZ5ucyeHopZXpaN5zLPyucfZXaa/5ksT4eNj5ts/Wf2mi2KyWz5M2uelFnvKjspb2fNblb2b8t@/7HoZu3W/c3g7rr5kpfNi@Zs3uwMs9H4st3J3lej6eWouPz1sHg9O2uNb9qLednpnd/9fppM8z76j8OXj9/9t7d25330fTgqrkbj61FxsX5sPFy//stjkS9axU3r/u5qNO197Q66vfPVCm7908DHz/ryeeekS8Ph89a7bJ6rL3UOh123d/Kuuw2kzWsGQDLAmQaox4L4ZvFYvrOMY@32Qew89V1tD2z@zS31DADowG43h4sYgGrUkbir@ER4LAfGr/ZS5wHEMACHNbqztht4S6FCexMDebuqAYhkU@RYwekEKMiZ4j8fLE1ClvRELLAg4QIiYWqQQlq0ZFuDjKWgTWBABCGI3OJAyCY3kwURSMG0Nam@amnoHd3ILT9aDmx95eHCMAwVgoANVWTByupIJSQylmJDl5qGEYCp0gGaX8FyrLwd4QE9BL4B6bkF21YdWeDTUNwOfBqCwADvLF0@@lnAFXgbAwcDLI7dr7E5NgJtiWNFOo5xLBxZ4GGTq8yGSCBORWxU6yvj122YQGoXWXLX4IIqBpIbEykEQbRcPG9U1VQP7KetjkUWlO5J5i3ocDFLoIwsg7lh1YoItLmSYYIwLPCwbXU8yXt2gLBVDH5UZagyBwYJxKoL0cM4xlkBF8BK7gRohwjXpS6OancAFdq0eKIMsLunWiVkdvVokBH7oTBioa2LfWc3/eIaywPp8wGwJUPLrb0SQWIpViUZbN/LFBcwjJaGln6lE2aPLBrazu63DiLMsqMu21i8aqUrFnxlqUbZhh6gEsYumsqbYw2fqgdS5aNL1oRa3tTqK61ddJL3OZZXGQl@Be8sRhVz40@wIQi5zXZWiiIibIU9yPKaKKhlRc8t6RJOUVLwqtUs8JJMrEAwprr0TNPWWb5wpfoCZ89f4eiEgaMVfKgHaKWJhDrgGGg7tmQwBoSzbyZhiHG9LYdrA4q1K6zvBZs1CWMPMBkLM1XVnlsMiF4AwHyL0@YujAd2r6SLpibbakv5RtrxDOMcbyvfcxMe8PmCZBikjj3oLyaGKjarZfS7oSkfD10crV/VubbEsTHeqrIhN64nOnl55gVN7NtkdFAiqZ0RGOZm5trVT7ccBujPS9qAsLIUdBbsAks4i4a2PKiEXjISo3XMB4vYVDe1aps9anWGgP@YFYcMs9/uyKZfJM7drsRADS6h6Td5uN6c4jg9IO36d75YTuazctUbDB7@AQ "Perl 5 – Try It Online"

# [Perl 5], 96 bytes
Read stdin. Exits 1 if net, 0 if not.
```bash
perl -00ae'@l=@r=map{++$c[$-[0]]while/#/g;y/#//||()}@F;@r>@c?@r:@l=@c;exit!grep$r[$_]>@l-2,0,-1'
```
When oriented with longer side vertical as shown in the challenge:
* nets have height 4 or 5
* nets never start or end with a "long" column (2+ for height 3; 3+ for height 4; 4+ for height 5) but non-nets always do
* for non-nets of height 3 the squares may not be connected when the other orientation is chosen
This simplifies to:
* non-nets have an start or end column containing more than height-2 squares
```
printf "%s\n" '...#..' '####..' '...#..' '......' '......' '......' |
# -00 slurps records in paragraph mode
# -a loops over records, with lines stored in @F
perl -00ae'
# compute array of non-zero counts of rows
# initialise length direction to horizontal
# "row" counts will be compared to length, so
# switch either @r or @l to other direction below
@l = @r = map {
# part-compute array of non-zero counts of columns
++$c[ $-[0] ] while /#/g;
y/#// || ()
} @F;
# set length to vertical if appropriate
# or use columns for counts
@r>@c ? @r : @l
= @c;
# test if start or end count is out of range
# exit with the negation to save a character
exit ! grep $r[$_]>@l-2, 0,-1
'
echo $?
```
[Try it online!][TIO-mq35wp24]
[Perl 5]: https://www.perl.org/
[TIO-mq35wp24]: https://tio.run/##pVldT9tAEHzPr3AzQYBILmmlvhABfuqfAIQgciFSGiI7qEXAX2@ahHz4znu7cykPGKPzeW93dmd2PSvKyfcFsnlRzbOn@3JaVFXrpSqy6uWhyo6LP@P58bC1vMlWf2Zv2awcT@c/s/ZRlfUus6PqZtruZlX/pur3H8tudtK5ux7cXrVfi6p93p4@t0@HWT66ODnNPhb55CIvL37dz97Ozjqj605vufL299N4UvTRfxy@Ln/3399PTj/yH8O8vMxHV3l5vnpoNFy9/MtjWcw65XXn7vYyn/S@dQfd3tfFAm7108LyZ3X5vHPSpeXweetd1s81lzqH/a6bO3nX7QbS5g0DIBngTAPUY0F8s3gs31nGsbb7IHae5q62B9b/5pZ6BgB0YDebw0UMQD3qSNxVfCI8lgPjV3up8wBiGID9Gt1Zmw28pVChvY6BvF3dAESyKXKs4HQCFORM8Z8PliYhS3oiFliQcAGRMA1IIS1asq1BxlLQJjAgghBEbnEgZJObyYIIpGDamlRftTT0jm7klh8tB7a@8nBhGIYKQcCGKrJgZXWkEhIZS7GhS03DCMBU6QDNr2A5Vt6O8IAeAt@A9NyCbauOLPBpKG4HPg1BYIB3li4f/SzgCryNgb0BFsfu1tgcG4G2xLEiHcc4Fo4s8LDJVWZDJBCnIjbq9ZXx6yZMILWLLLkbcEEdA8mNiRSCIFounjeqamoG9tNWxyILSvck8xZ0uJglUEaWwdywakUE2lzJMEEYFnjYtjqe5D07QNgqBj@qMlSZA4MEYtWF6GEc46yAC2AldwK0Q4TrUhcHtTuACm1aPFEG2N1ToxIyu3o0yIj9UBix0NbFvrObfnGN5YH0@QDYkqHl1k6JILEUq5IMtu9ligsYRktDS7/SCbNDFg1tZ/dbexFm2dGUbSxetdIVC76yVKNsQw9QCWMXTeXNsYZP1QOp8tEla0Itbxr1ldYuOsn7HMurjAS/gncWo4q58SfYEITcZjsrRRERtsIeZHlNFNSyoueWdAmnKCl41WoWeEkmViAYU116pmnrLF@4Un2Bs@evcHTCwNEKPtQDtNJEQh1wDLQdWzIYA8LZN5MwxLjelsONAcXKFdb3gvWahLEHmIyFmapqzy0GRC8AYL7FaXMXxgPbV9JFU5NtjaV8I@14hnGOt5XvuQkP@HxBMgxSxx70FxNDFZvVMvrd0JSP@y6O1q/qXFvi2Bhv1dmQG9cTnbw884Im9m0y2iuR1M4IDHMzc@36p1sOA/TnJW1AWFsKOgu2gSWcRUNbHlRCLxmJ0Trkg0Vsqptatc0etT5DwH/MikOG2W13YNMvEud2V2KgBpfQ9Js83GxOcZgekHb9@zybj5@n1aI3GNz/Aw "Perl 5 – Try It Online"

#7: Post edited by

jhnc‭ · 2026-05-31T13:03:25Z (4 months ago)
improve comments

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# [Perl 5], 98 bytes
Read stdin. Exits 1 if net, 0 if not.
```bash
perl -00ae'@l=@r=map{++$c[(pos)-1]while/#/g;y/#//||()}@F;@r>@c?@r:@l=@c;exit!grep$r[$_]>@l-2,0,-1'
```
When oriented with longer side vertical as shown in the challenge:
* nets have height 4 or 5
* nets never start or end with a "long" column (2+ for height 3; 3+ for height 4; 4+ for height 5) but non-nets always do
* for non-nets of height 3 the squares may not be connected when the other orientation is chosen
This simplifies to:
* non-nets have an start or end column containing more than height-2 squares
```
printf "%s\n" '...#..' '####..' '...#..' '......' '......' '......' |
# -00 slurps records in paragraph mode
# -a loops over records, with lines stored in @F
perl -00ae'
# compute array of non-zero counts of rows
# default length direction to vertical
@l = @r = map {
# part-compute array of non-zero counts of columns
++$c[(pos)-1] while /#/g;
y/#// || ()
} @F;
~~# set length to longer direction if appropriate~~
~~# use the other direction for counts~~
@r>@c ? @r : @l
= @c;
# test if start or end count is out of range
# exit with the negation to save a character
exit ! grep $r[$_]>@l-2, 0,-1
'
echo $?
```
[Try it online!][TIO-mptr86vk]
[Perl 5]: https://www.perl.org/
[TIO-mptr86vk]: https://tio.run/##pVldT9tAEHzPr3AzQSQiuYRKfSEC8tQ/AQjRyIVIaRLZQS0C/npTEvLhO@/tzqU8YIzO573d2Z3Z9SIvpt9WyJZ5ucyeHopZXpaN5zLPyucfZXaa/5ksT4eNj5ts/Wf2mi2KyWz5M2uelFnvKjspb2fNblb2b8t@/7HoZu3W/c3g7rr5kpfNi@Zs3uwMs9H4st3J3lej6eWouPz1sHg9O2uNb9qLednpnd/9fppM8z76j8OXj9/9t7d25330fTgqrkbj61FxsX5sPFy//stjkS9axU3r/u5qNO197Q66vfPVCm7908DHz/ryeeekS8Ph89a7bJ6rL3UOh123d/Kuuw2kzWsGQDLAmQaox4L4ZvFYvrOMY@32Qew89V1tD2z@zS31DADowG43h4sYgGrUkbir@ER4LAfGr/ZS5wHEMACHNbqztht4S6FCexMDebuqAYhkU@RYwekEKMiZ4j8fLE1ClvRELLAg4QIiYWqQQlq0ZFuDjKWgTWBABCGI3OJAyCY3kwURSMG0Nam@amnoHd3ILT9aDmx95eHCMAwVgoANVWTByupIJSQylmJDl5qGEYCp0gGaX8FyrLwd4QE9BL4B6bkF21YdWeDTUNwOfBqCwADvLF0@@lnAFXgbAwcDLI7dr7E5NgJtiWNFOo5xLBxZ4GGTq8yGSCBORWxU6yvj122YQGoXWXLX4IIqBpIbEykEQbRcPG9U1VQP7KetjkUWlO5J5i3ocDFLoIwsg7lh1YoItLmSYYIwLPCwbXU8yXt2gLBVDH5UZagyBwYJxKoL0cM4xlkBF8BK7gRohwjXpS6OancAFdq0eKIMsLunWiVkdvVokBH7oTBioa2LfWc3/eIaywPp8wGwJUPLrb0SQWIpViUZbN/LFBcwjJaGln6lE2aPLBrazu63DiLMsqMu21i8aqUrFnxlqUbZhh6gEsYumsqbYw2fqgdS5aNL1oRa3tTqK61ddJL3OZZXGQl@Be8sRhVz40@wIQi5zXZWiiIibIU9yPKaKKhlRc8t6RJOUVLwqtUs8JJMrEAwprr0TNPWWb5wpfoCZ89f4eiEgaMVfKgHaKWJhDrgGGg7tmQwBoSzbyZhiHG9LYdrA4q1K6zvBZs1CWMPMBkLM1XVnlsMiF4AwHyL0@YujAd2r6SLpibbakv5RtrxDOMcbyvfcxMe8PmCZBikjj3oLyaGKjarZfS7oSkfD10crV/VubbEsTHeqrIhN64nOnl55gVN7NtkdFAiqZ0RGOZm5trVT7ccBujPS9qAsLIUdBbsAks4i4a2PKiEXjISo3XMB4vYVDe1aps9anWGgP@YFYcMs9/uyKZfJM7drsRADS6h6Td5uN6c4jg9IO36d75YTuazctUbDB7@AQ "Perl 5 – Try It Online"

# [Perl 5], 98 bytes
Read stdin. Exits 1 if net, 0 if not.
```bash
perl -00ae'@l=@r=map{++$c[(pos)-1]while/#/g;y/#//||()}@F;@r>@c?@r:@l=@c;exit!grep$r[$_]>@l-2,0,-1'
```
When oriented with longer side vertical as shown in the challenge:
* nets have height 4 or 5
* nets never start or end with a "long" column (2+ for height 3; 3+ for height 4; 4+ for height 5) but non-nets always do
* for non-nets of height 3 the squares may not be connected when the other orientation is chosen
This simplifies to:
* non-nets have an start or end column containing more than height-2 squares
```
printf "%s\n" '...#..' '####..' '...#..' '......' '......' '......' |
# -00 slurps records in paragraph mode
# -a loops over records, with lines stored in @F
perl -00ae'
# compute array of non-zero counts of rows
# initialise length direction to horizontal
# because "row" counts will be compared to length,
# switch either @r or @l to other direction below
@l = @r = map {
# part-compute array of non-zero counts of columns
++$c[(pos)-1] while /#/g;
y/#// || ()
} @F;
# set length to vertical if appropriate
# or use columns for counts
@r>@c ? @r : @l
= @c;
# test if start or end count is out of range
# exit with the negation to save a character
exit ! grep $r[$_]>@l-2, 0,-1
'
echo $?
```
[Try it online!][TIO-mptr86vk]
[Perl 5]: https://www.perl.org/
[TIO-mptr86vk]: https://tio.run/##pVldT9tAEHzPr3AzQSQiuYRKfSEC8tQ/AQjRyIVIaRLZQS0C/npTEvLhO@/tzqU8YIzO573d2Z3Z9SIvpt9WyJZ5ucyeHopZXpaN5zLPyucfZXaa/5ksT4eNj5ts/Wf2mi2KyWz5M2uelFnvKjspb2fNblb2b8t@/7HoZu3W/c3g7rr5kpfNi@Zs3uwMs9H4st3J3lej6eWouPz1sHg9O2uNb9qLednpnd/9fppM8z76j8OXj9/9t7d25330fTgqrkbj61FxsX5sPFy//stjkS9axU3r/u5qNO197Q66vfPVCm7908DHz/ryeeekS8Ph89a7bJ6rL3UOh123d/Kuuw2kzWsGQDLAmQaox4L4ZvFYvrOMY@32Qew89V1tD2z@zS31DADowG43h4sYgGrUkbir@ER4LAfGr/ZS5wHEMACHNbqztht4S6FCexMDebuqAYhkU@RYwekEKMiZ4j8fLE1ClvRELLAg4QIiYWqQQlq0ZFuDjKWgTWBABCGI3OJAyCY3kwURSMG0Nam@amnoHd3ILT9aDmx95eHCMAwVgoANVWTByupIJSQylmJDl5qGEYCp0gGaX8FyrLwd4QE9BL4B6bkF21YdWeDTUNwOfBqCwADvLF0@@lnAFXgbAwcDLI7dr7E5NgJtiWNFOo5xLBxZ4GGTq8yGSCBORWxU6yvj122YQGoXWXLX4IIqBpIbEykEQbRcPG9U1VQP7KetjkUWlO5J5i3ocDFLoIwsg7lh1YoItLmSYYIwLPCwbXU8yXt2gLBVDH5UZagyBwYJxKoL0cM4xlkBF8BK7gRohwjXpS6OancAFdq0eKIMsLunWiVkdvVokBH7oTBioa2LfWc3/eIaywPp8wGwJUPLrb0SQWIpViUZbN/LFBcwjJaGln6lE2aPLBrazu63DiLMsqMu21i8aqUrFnxlqUbZhh6gEsYumsqbYw2fqgdS5aNL1oRa3tTqK61ddJL3OZZXGQl@Be8sRhVz40@wIQi5zXZWiiIibIU9yPKaKKhlRc8t6RJOUVLwqtUs8JJMrEAwprr0TNPWWb5wpfoCZ89f4eiEgaMVfKgHaKWJhDrgGGg7tmQwBoSzbyZhiHG9LYdrA4q1K6zvBZs1CWMPMBkLM1XVnlsMiF4AwHyL0@YujAd2r6SLpibbakv5RtrxDOMcbyvfcxMe8PmCZBikjj3oLyaGKjarZfS7oSkfD10crV/VubbEsTHeqrIhN64nOnl55gVN7NtkdFAiqZ0RGOZm5trVT7ccBujPS9qAsLIUdBbsAks4i4a2PKiEXjISo3XMB4vYVDe1aps9anWGgP@YFYcMs9/uyKZfJM7drsRADS6h6Td5uN6c4jg9IO36d75YTuazctUbDB7@AQ "Perl 5 – Try It Online"

#6: Post edited by

jhnc‭ · 2026-05-31T12:49:12Z (4 months ago)
fixes typos in explanatory version

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# [Perl 5], 98 bytes
Read stdin. Exits 1 if net, 0 if not.
```bash
perl -00ae'@l=@r=map{++$c[(pos)-1]while/#/g;y/#//||()}@F;@r>@c?@r:@l=@c;exit!grep$r[$_]>@l-2,0,-1'
```
When oriented with longer side vertical as shown in the challenge:
* nets have height 4 or 5
* nets never start or end with a "long" column (2+ for height 3; 3+ for height 4; 4+ for height 5) but non-nets always do
* for non-nets of height 3 the squares may not be connected when the other orientation is chosen
This simplifies to:
* non-nets have an start or end column containing more than height-2 squares
```
printf "%s\n" '...#..' '####..' '...#..' '......' '......' '......' |
# -00 slurps records in paragraph mode
# -a loops over records, with lines stored in @F
perl -00ae'
# compute array of non-zero counts of rows
# default length direction to vertical
@l = @r = map {
# part-compute array of non-zero counts of columns
++$c[(pos)-1] while /#/g;
y/#// || ()
} @F;
# set length to longer direction if appropriate
# use the other direction for counts
@r>@c ? @r : @l
= @c;
# test if start or end count is out of range
# exit with the negation to save a character
~~exit ! grep $c[$_]>$l-2, 0,-1~~
'
echo $?
```
[Try it online!][TIO-mptr86vk]
[Perl 5]: https://www.perl.org/
[TIO-mptr86vk]: https://tio.run/##pVldT9tAEHzPr3AzQSQiuYRKfSEC8tQ/AQjRyIVIaRLZQS0C/npTEvLhO@/tzqU8YIzO573d2Z3Z9SIvpt9WyJZ5ucyeHopZXpaN5zLPyucfZXaa/5ksT4eNj5ts/Wf2mi2KyWz5M2uelFnvKjspb2fNblb2b8t@/7HoZu3W/c3g7rr5kpfNi@Zs3uwMs9H4st3J3lej6eWouPz1sHg9O2uNb9qLednpnd/9fppM8z76j8OXj9/9t7d25330fTgqrkbj61FxsX5sPFy//stjkS9axU3r/u5qNO197Q66vfPVCm7908DHz/ryeeekS8Ph89a7bJ6rL3UOh123d/Kuuw2kzWsGQDLAmQaox4L4ZvFYvrOMY@32Qew89V1tD2z@zS31DADowG43h4sYgGrUkbir@ER4LAfGr/ZS5wHEMACHNbqztht4S6FCexMDebuqAYhkU@RYwekEKMiZ4j8fLE1ClvRELLAg4QIiYWqQQlq0ZFuDjKWgTWBABCGI3OJAyCY3kwURSMG0Nam@amnoHd3ILT9aDmx95eHCMAwVgoANVWTByupIJSQylmJDl5qGEYCp0gGaX8FyrLwd4QE9BL4B6bkF21YdWeDTUNwOfBqCwADvLF0@@lnAFXgbAwcDLI7dr7E5NgJtiWNFOo5xLBxZ4GGTq8yGSCBORWxU6yvj122YQGoXWXLX4IIqBpIbEykEQbRcPG9U1VQP7KetjkUWlO5J5i3ocDFLoIwsg7lh1YoItLmSYYIwLPCwbXU8yXt2gLBVDH5UZagyBwYJxKoL0cM4xlkBF8BK7gRohwjXpS6OancAFdq0eKIMsLunWiVkdvVokBH7oTBioa2LfWc3/eIaywPp8wGwJUPLrb0SQWIpViUZbN/LFBcwjJaGln6lE2aPLBrazu63DiLMsqMu21i8aqUrFnxlqUbZhh6gEsYumsqbYw2fqgdS5aNL1oRa3tTqK61ddJL3OZZXGQl@Be8sRhVz40@wIQi5zXZWiiIibIU9yPKaKKhlRc8t6RJOUVLwqtUs8JJMrEAwprr0TNPWWb5wpfoCZ89f4eiEgaMVfKgHaKWJhDrgGGg7tmQwBoSzbyZhiHG9LYdrA4q1K6zvBZs1CWMPMBkLM1XVnlsMiF4AwHyL0@YujAd2r6SLpibbakv5RtrxDOMcbyvfcxMe8PmCZBikjj3oLyaGKjarZfS7oSkfD10crV/VubbEsTHeqrIhN64nOnl55gVN7NtkdFAiqZ0RGOZm5trVT7ccBujPS9qAsLIUdBbsAks4i4a2PKiEXjISo3XMB4vYVDe1aps9anWGgP@YFYcMs9/uyKZfJM7drsRADS6h6Td5uN6c4jg9IO36d75YTuazctUbDB7@AQ "Perl 5 – Try It Online"

# [Perl 5], 98 bytes
Read stdin. Exits 1 if net, 0 if not.
```bash
perl -00ae'@l=@r=map{++$c[(pos)-1]while/#/g;y/#//||()}@F;@r>@c?@r:@l=@c;exit!grep$r[$_]>@l-2,0,-1'
```
When oriented with longer side vertical as shown in the challenge:
* nets have height 4 or 5
* nets never start or end with a "long" column (2+ for height 3; 3+ for height 4; 4+ for height 5) but non-nets always do
* for non-nets of height 3 the squares may not be connected when the other orientation is chosen
This simplifies to:
* non-nets have an start or end column containing more than height-2 squares
```
printf "%s\n" '...#..' '####..' '...#..' '......' '......' '......' |
# -00 slurps records in paragraph mode
# -a loops over records, with lines stored in @F
perl -00ae'
# compute array of non-zero counts of rows
# default length direction to vertical
@l = @r = map {
# part-compute array of non-zero counts of columns
++$c[(pos)-1] while /#/g;
y/#// || ()
} @F;
# set length to longer direction if appropriate
# use the other direction for counts
@r>@c ? @r : @l
= @c;
# test if start or end count is out of range
# exit with the negation to save a character
exit ! grep $r[$_]>@l-2, 0,-1
'
echo $?
```
[Try it online!][TIO-mptr86vk]
[Perl 5]: https://www.perl.org/
[TIO-mptr86vk]: https://tio.run/##pVldT9tAEHzPr3AzQSQiuYRKfSEC8tQ/AQjRyIVIaRLZQS0C/npTEvLhO@/tzqU8YIzO573d2Z3Z9SIvpt9WyJZ5ucyeHopZXpaN5zLPyucfZXaa/5ksT4eNj5ts/Wf2mi2KyWz5M2uelFnvKjspb2fNblb2b8t@/7HoZu3W/c3g7rr5kpfNi@Zs3uwMs9H4st3J3lej6eWouPz1sHg9O2uNb9qLednpnd/9fppM8z76j8OXj9/9t7d25330fTgqrkbj61FxsX5sPFy//stjkS9axU3r/u5qNO197Q66vfPVCm7908DHz/ryeeekS8Ph89a7bJ6rL3UOh123d/Kuuw2kzWsGQDLAmQaox4L4ZvFYvrOMY@32Qew89V1tD2z@zS31DADowG43h4sYgGrUkbir@ER4LAfGr/ZS5wHEMACHNbqztht4S6FCexMDebuqAYhkU@RYwekEKMiZ4j8fLE1ClvRELLAg4QIiYWqQQlq0ZFuDjKWgTWBABCGI3OJAyCY3kwURSMG0Nam@amnoHd3ILT9aDmx95eHCMAwVgoANVWTByupIJSQylmJDl5qGEYCp0gGaX8FyrLwd4QE9BL4B6bkF21YdWeDTUNwOfBqCwADvLF0@@lnAFXgbAwcDLI7dr7E5NgJtiWNFOo5xLBxZ4GGTq8yGSCBORWxU6yvj122YQGoXWXLX4IIqBpIbEykEQbRcPG9U1VQP7KetjkUWlO5J5i3ocDFLoIwsg7lh1YoItLmSYYIwLPCwbXU8yXt2gLBVDH5UZagyBwYJxKoL0cM4xlkBF8BK7gRohwjXpS6OancAFdq0eKIMsLunWiVkdvVokBH7oTBioa2LfWc3/eIaywPp8wGwJUPLrb0SQWIpViUZbN/LFBcwjJaGln6lE2aPLBrazu63DiLMsqMu21i8aqUrFnxlqUbZhh6gEsYumsqbYw2fqgdS5aNL1oRa3tTqK61ddJL3OZZXGQl@Be8sRhVz40@wIQi5zXZWiiIibIU9yPKaKKhlRc8t6RJOUVLwqtUs8JJMrEAwprr0TNPWWb5wpfoCZ89f4eiEgaMVfKgHaKWJhDrgGGg7tmQwBoSzbyZhiHG9LYdrA4q1K6zvBZs1CWMPMBkLM1XVnlsMiF4AwHyL0@YujAd2r6SLpibbakv5RtrxDOMcbyvfcxMe8PmCZBikjj3oLyaGKjarZfS7oSkfD10crV/VubbEsTHeqrIhN64nOnl55gVN7NtkdFAiqZ0RGOZm5trVT7ccBujPS9qAsLIUdBbsAks4i4a2PKiEXjISo3XMB4vYVDe1aps9anWGgP@YFYcMs9/uyKZfJM7drsRADS6h6Td5uN6c4jg9IO36d75YTuazctUbDB7@AQ "Perl 5 – Try It Online"

#5: Post edited by

jhnc‭ · 2026-05-31T12:37:07Z (4 months ago)
rename variables to improve clarity; using array (@l) instead of scalar ($m) allows more efficient ternary

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~~# [Perl 5], 109 bytes~~
Read stdin. Exits 1 if net, 0 if not.
```bash
perl -00ae'@a=map{++$b[(pos)-1]while/#/g;y/#//||()}@F;$m=@a>@b?@a:@b;@a=@b
if@a>@b;exit!grep$a[$_]>$m-2,0,-1'
```
When oriented with longer side vertical as shown in the challenge:
* nets have height 4 or 5
* nets never start or end with a "long" column (2+ for height 3; 3+ for height 4; 4+ for height 5) but non-nets always do
* for non-nets of height 3 the squares may not be connected when the other orientation is chosen
This simplifies to:
* non-nets have an start or end column containing more than height-2 squares
```
printf "%s\n" '...#..' '####..' '...#..' '......' '......' '......' |
# -00 slurps records in paragraph mode
# -a loops over records, with lines stored in @F
perl -00ae'
~~# compute array of non-zero counts in rows~~
~~@a = map {~~
~~# compute part of array of non-zero counts in columns~~
~~++$b[(pos)-1] while /#/g;~~
y/#// || ()
} @F;
~~# get length of longer direction~~
~~$m = @a>@b ? @a : @b;~~
~~# use other direction for counts~~
~~@a = @b if @a>@b;~~
# test if start or end count is out of range
# exit with the negation to save a character
~~exit ! grep $a[$_]>$m-2, 0,-1~~
'
echo $?
```
~~[Try it online!][TIO-mptcu20d]~~
[Perl 5]: https://www.perl.org/
[TIO-mptcu20d]: https://tio.run/##pVnRTiJBEHznK/YoLkKEAS@5F4m6T/cTagwkq5IoEBZzZ9RfPw4QZGe2p7uG48F1yezQ013dVd07LxZPP1fIlkW5zB5Hi2lRlo2XssjKl3GZnRR/JsuTYWN9k23@zd6y@WIyXd5nze9l1rvMvpc302Y3K/s3Zb//sOhm7dbd9eD2qvlalM3z5nTW7AyzfHzR7mQfq3x08Tyav52etsbX7fms7PTObn8/Tp6KPvoPw9f13/77e7vzkf8atp4v8tFlPr7KR@f5eLh@Mh83Jvfb74YbS749LIp5a3Tduru9bD33fnQH3d7ZagW3@TSw/mwun3dOujQcPm@9y/a5@lLncNh1dyfvut9A2rxmACQDnGmAeiyIvywey3eWcaz9Poidp76r7YHt19xSzwCADuxuc7iIAahGHYm7ik@Ex3Jg/GovdR5ADANwWKM7a7eBtxQqtLcxkLerGoBINkWOFZxOgIKcKf7zwdIkZElPxAILEi4gEqYGKaRFS7Y1yFgK2gQGRBCCyC0OhGxyM1kQgRRMW5Pqq5aG3tGN3PKj5cDWVx4uDMNQIQjYUEUWrKyOVEIiYyk2dKlpGAGYKh2g@RUsx8rbER7QQ@AbkJ5bsG3VkQU@DcXtwKchCAzwztLlo58FXIG3MXAwwOLYrzU2x0agLXGsSMcxjoUjCzxscpXZEAnEqYiNan1l/LoLE0jtIkvuGlxQxUByYyKFIIiWi@eNqprqgf201bHIgtI9ybwFHS5mCZSRZTA3rFoRgTZXMkwQhgUetq2OJ3nPDhC2isGPqgxV5sAggVh1IXoYxzgr4AJYyZ0A7RDhutTFUe0OoEKbFk@UAXb3VKuEzK4eDTJiPxRGLLR1se/spl9cY3kgfT4AtmRoufWlRJBYilVJBtv3MsUFDKOloaVf6YT5QhYNbWf3WwcRZtlRl20sXrXSFQu@slSjbEMPUAljF03ll2MNn6oHUuWjS9aEWt7U6iutXXSS9zmWVxkJfgXvLEYVc@NPsCEIuc12VooiImyFPcjymiioZUXPLekSTlFS8KrVLPCSTKxAMKa69EzT1lm@cKX6AmfPX@HohIGjFXyoB2iliYQ64BhoO7ZkMAaEs28mYYhxvS2HawOKjSus9wXbNQljDzAZCzNV1Z5bDIheAMC8i9PmLowH9j9JF01NttWW8o204xnGOd5WvucmPODzBckwSB170G9MDFVsVsvoe0NTPh66OFq/qnNtiWNjvFVlQ25cT3Ty8swLmti3yeigRFI7IzDMzcy1q69uOQzQr5e0AWFlKegs2AeWcBYNbXlQCb1kJEbrmBcWsaluatU2e9TqDAH/MSsOGeZruyObfpE497sSAzW4hKbf5OF6c4rj9IC069/ZfDmZTctVbzAY/QM "Perl 5 – Try It Online"

# [Perl 5], 98 bytes
Read stdin. Exits 1 if net, 0 if not.
```bash
perl -00ae'@l=@r=map{++$c[(pos)-1]while/#/g;y/#//||()}@F;@r>@c?@r:@l=@c;exit!grep$r[$_]>@l-2,0,-1'
```
When oriented with longer side vertical as shown in the challenge:
* nets have height 4 or 5
* nets never start or end with a "long" column (2+ for height 3; 3+ for height 4; 4+ for height 5) but non-nets always do
* for non-nets of height 3 the squares may not be connected when the other orientation is chosen
This simplifies to:
* non-nets have an start or end column containing more than height-2 squares
```
printf "%s\n" '...#..' '####..' '...#..' '......' '......' '......' |
# -00 slurps records in paragraph mode
# -a loops over records, with lines stored in @F
perl -00ae'
# compute array of non-zero counts of rows
# default length direction to vertical
@l = @r = map {
# part-compute array of non-zero counts of columns
++$c[(pos)-1] while /#/g;
y/#// || ()
} @F;
# set length to longer direction if appropriate
# use the other direction for counts
@r>@c ? @r : @l
= @c;
# test if start or end count is out of range
# exit with the negation to save a character
exit ! grep $c[$_]>$l-2, 0,-1
'
echo $?
```
[Try it online!][TIO-mptr86vk]
[Perl 5]: https://www.perl.org/
[TIO-mptr86vk]: https://tio.run/##pVldT9tAEHzPr3AzQSQiuYRKfSEC8tQ/AQjRyIVIaRLZQS0C/npTEvLhO@/tzqU8YIzO573d2Z3Z9SIvpt9WyJZ5ucyeHopZXpaN5zLPyucfZXaa/5ksT4eNj5ts/Wf2mi2KyWz5M2uelFnvKjspb2fNblb2b8t@/7HoZu3W/c3g7rr5kpfNi@Zs3uwMs9H4st3J3lej6eWouPz1sHg9O2uNb9qLednpnd/9fppM8z76j8OXj9/9t7d25330fTgqrkbj61FxsX5sPFy//stjkS9axU3r/u5qNO197Q66vfPVCm7908DHz/ryeeekS8Ph89a7bJ6rL3UOh123d/Kuuw2kzWsGQDLAmQaox4L4ZvFYvrOMY@32Qew89V1tD2z@zS31DADowG43h4sYgGrUkbir@ER4LAfGr/ZS5wHEMACHNbqztht4S6FCexMDebuqAYhkU@RYwekEKMiZ4j8fLE1ClvRELLAg4QIiYWqQQlq0ZFuDjKWgTWBABCGI3OJAyCY3kwURSMG0Nam@amnoHd3ILT9aDmx95eHCMAwVgoANVWTByupIJSQylmJDl5qGEYCp0gGaX8FyrLwd4QE9BL4B6bkF21YdWeDTUNwOfBqCwADvLF0@@lnAFXgbAwcDLI7dr7E5NgJtiWNFOo5xLBxZ4GGTq8yGSCBORWxU6yvj122YQGoXWXLX4IIqBpIbEykEQbRcPG9U1VQP7KetjkUWlO5J5i3ocDFLoIwsg7lh1YoItLmSYYIwLPCwbXU8yXt2gLBVDH5UZagyBwYJxKoL0cM4xlkBF8BK7gRohwjXpS6OancAFdq0eKIMsLunWiVkdvVokBH7oTBioa2LfWc3/eIaywPp8wGwJUPLrb0SQWIpViUZbN/LFBcwjJaGln6lE2aPLBrazu63DiLMsqMu21i8aqUrFnxlqUbZhh6gEsYumsqbYw2fqgdS5aNL1oRa3tTqK61ddJL3OZZXGQl@Be8sRhVz40@wIQi5zXZWiiIibIU9yPKaKKhlRc8t6RJOUVLwqtUs8JJMrEAwprr0TNPWWb5wpfoCZ89f4eiEgaMVfKgHaKWJhDrgGGg7tmQwBoSzbyZhiHG9LYdrA4q1K6zvBZs1CWMPMBkLM1XVnlsMiF4AwHyL0@YujAd2r6SLpibbakv5RtrxDOMcbyvfcxMe8PmCZBikjj3oLyaGKjarZfS7oSkfD10crV/VubbEsTHeqrIhN64nOnl55gVN7NtkdFAiqZ0RGOZm5trVT7ccBujPS9qAsLIUdBbsAks4i4a2PKiEXjISo3XMB4vYVDe1aps9anWGgP@YFYcMs9/uyKZfJM7drsRADS6h6Td5uN6c4jg9IO36d75YTuazctUbDB7@AQ "Perl 5 – Try It Online"

#4: Post edited by

jhnc‭ · 2026-05-31T05:50:41Z (4 months ago)
we can get position without using explicit counter

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~~# [Perl 5], 118 bytes~~
Read stdin. Exits 1 if net, 0 if not.
```bash
~~perl -00ae'@a=map{for$i(0..5){/^.{$i}#/&&$b[$i]++}y/#//||()}@F;$m=@a>@b?@a:@b;@a=@b~~
if@a>@b;exit!grep$a[$_]>$m-2,0,-1'
```
When oriented with longer side vertical as shown in the challenge:
* nets have height 4 or 5
* nets never start or end with a "long" column (2+ for height 3; 3+ for height 4; 4+ for height 5) but non-nets always do
* for non-nets of height 3 the squares may not be connected when the other orientation is chosen
This simplifies to:
* non-nets have an start or end column containing more than height-2 squares
```
printf "%s\n" '...#..' '####..' '...#..' '......' '......' '......' |
# -00 slurps records in paragraph mode
# -a loops over records, with lines stored in @F
perl -00ae'
~~# array of non-zero counts in rows~~
@a = map {
~~# array of non-zero counts in columns~~
~~for $i (0..5) {~~
~~/^.{$i}#/ && $b[$i]++~~
}
y/#// || ()
} @F;
# get length of longer direction
$m = @a>@b ? @a : @b;
# use other direction for counts
@a = @b if @a>@b;
# test if start or end count is out of range
# exit with the negation to save a character
exit ! grep $a[$_]>$m-2, 0,-1
'
echo $?
```
~~[Try it online!][TIO-mptbi5b6]~~
[Perl 5]: https://www.perl.org/
[TIO-mptbi5b6]: https://tio.run/##pVldb9pQDH3nV2ScrAUVbtikvhS1zdP@RNtVINEOaQVEqLSK8tfHCuUjufG1z2V9SYMuxrGPfY6d2Wj@@3KNZDEqFsmvwXwyKorGazFKitdhkZyP/owX5/3Gx02y@TdZJrP5eLJ4Sppfi6R7k3wt7ifNTlJk90WWPc87SSt9vOs93DbfRkXzqjmZNtv9JB9et9rJap0Prl8Gs@XTdJ6OWz3nLtvL7KdbpuMVsrOzdHiXjh8uLlZvGbLs/b3VXuU/@unLdT64yYe3@eAqH/Y/TOTDxvhp@1l/49KX5/lolg7u0seHm/Sl@73T63S/rddwm78GPv42l887J10aDp@3lcv2e/WjzuFodXcnW90bkIzXHIDkgDMdUB8L4i@Lj1UNlvFYezsIPU/dqh2B7cfc0YoDAJ3YnXG4gAMoZx2RVsVv@I/lwMTVPuoqADEcwPGMHqydgcpRqNDe5kA2V3YAgWoKPJb3dAIU5Eqpft87GoUs6RuhxIKEC4iCqUEKcdmSffUqloI2gQERhCBqiwMhW9xMFQQgBdPXqP6qlWHl0Y3aqmbLge2vPFwYhqFS4LGhiixYVR3ohETFUmzoYsswADBVOkCLK1iOlc0REdBTUHUgvrZg@6ojC3wZiubAlyEIDPDB0uVjtQq4Bm9j4OiAxbGHMzbHBqAtcaxIxyGOhSMbPGxyldkQEcSpiI1yf2XiuksTSO0iS@4aXFDGQPRgIqXAy5YL142qmuqJ/fTVsciCMj3JvAUdLmYLlJFlMDesXhGANtcyTBD6DR62r44n@YofIHwVkx9UGarMgUECoe5CzDCOCZbHBbCKOwLaPsJ1qYuTxh1AhTYtnigH7Omp1gkZqxUaZMS@L4xYaOti39lDv3jGikD8fgBsy9Bq66BEENmKVUkGO/YyxXkMo5WhpV/pgjkgi4a2s@etowiz/KjLNhavWusKJV85qlG2oQeogrGbpvLLoYFP1QOx8tFFa0Ktbmr9ldYuOslXOZZXGRFxBR8sRhVz60@wKfC5zQ5WjCIifIW9yKoMUVDbil5b0sXfosTgVetZ4CWZ2IFgbHXpnaats6rClZoLnL1/haMLBo5W8L4eoJUmIvqAY6Dt2JbBOODvvpmCIdb1thyuLSg2obDeF2zPRKw9wFQszFJVZ24xIXoDAPMuTtu7MBHY/yTdNDXZVjvKD9KOZxjneF/5mZuIQJUvSIZB7NqDfmNiqGKzWwbfG5ry8TjF0fpV3WtLHBvirTIbcut6YpKXd17QxL5NRkclEjsZgWFuZq9dfnXLYYB@vaQtCEtHQVfBPrFEsGhoy4tK6C0jMlunvLAIbXVju7Y5o5Z3CPiPXbHPMAdzJw79InHurRILNbiIod/k4fpwitP0gGT173S2GE8nxbrb6w3@AQ "Perl 5 – Try It Online"

# [Perl 5], 109 bytes
Read stdin. Exits 1 if net, 0 if not.
```bash
perl -00ae'@a=map{++$b[(pos)-1]while/#/g;y/#//||()}@F;$m=@a>@b?@a:@b;@a=@b
if@a>@b;exit!grep$a[$_]>$m-2,0,-1'
```
When oriented with longer side vertical as shown in the challenge:
* nets have height 4 or 5
* nets never start or end with a "long" column (2+ for height 3; 3+ for height 4; 4+ for height 5) but non-nets always do
* for non-nets of height 3 the squares may not be connected when the other orientation is chosen
This simplifies to:
* non-nets have an start or end column containing more than height-2 squares
```
printf "%s\n" '...#..' '####..' '...#..' '......' '......' '......' |
# -00 slurps records in paragraph mode
# -a loops over records, with lines stored in @F
perl -00ae'
# compute array of non-zero counts in rows
@a = map {
# compute part of array of non-zero counts in columns
++$b[(pos)-1] while /#/g;
y/#// || ()
} @F;
# get length of longer direction
$m = @a>@b ? @a : @b;
# use other direction for counts
@a = @b if @a>@b;
# test if start or end count is out of range
# exit with the negation to save a character
exit ! grep $a[$_]>$m-2, 0,-1
'
echo $?
```
[Try it online!][TIO-mptcu20d]
[Perl 5]: https://www.perl.org/
[TIO-mptcu20d]: https://tio.run/##pVnRTiJBEHznK/YoLkKEAS@5F4m6T/cTagwkq5IoEBZzZ9RfPw4QZGe2p7uG48F1yezQ013dVd07LxZPP1fIlkW5zB5Hi2lRlo2XssjKl3GZnRR/JsuTYWN9k23@zd6y@WIyXd5nze9l1rvMvpc302Y3K/s3Zb//sOhm7dbd9eD2qvlalM3z5nTW7AyzfHzR7mQfq3x08Tyav52etsbX7fms7PTObn8/Tp6KPvoPw9f13/77e7vzkf8atp4v8tFlPr7KR@f5eLh@Mh83Jvfb74YbS749LIp5a3Tduru9bD33fnQH3d7ZagW3@TSw/mwun3dOujQcPm@9y/a5@lLncNh1dyfvut9A2rxmACQDnGmAeiyIvywey3eWcaz9Poidp76r7YHt19xSzwCADuxuc7iIAahGHYm7ik@Ex3Jg/GovdR5ADANwWKM7a7eBtxQqtLcxkLerGoBINkWOFZxOgIKcKf7zwdIkZElPxAILEi4gEqYGKaRFS7Y1yFgK2gQGRBCCyC0OhGxyM1kQgRRMW5Pqq5aG3tGN3PKj5cDWVx4uDMNQIQjYUEUWrKyOVEIiYyk2dKlpGAGYKh2g@RUsx8rbER7QQ@AbkJ5bsG3VkQU@DcXtwKchCAzwztLlo58FXIG3MXAwwOLYrzU2x0agLXGsSMcxjoUjCzxscpXZEAnEqYiNan1l/LoLE0jtIkvuGlxQxUByYyKFIIiWi@eNqprqgf201bHIgtI9ybwFHS5mCZSRZTA3rFoRgTZXMkwQhgUetq2OJ3nPDhC2isGPqgxV5sAggVh1IXoYxzgr4AJYyZ0A7RDhutTFUe0OoEKbFk@UAXb3VKuEzK4eDTJiPxRGLLR1se/spl9cY3kgfT4AtmRoufWlRJBYilVJBtv3MsUFDKOloaVf6YT5QhYNbWf3WwcRZtlRl20sXrXSFQu@slSjbEMPUAljF03ll2MNn6oHUuWjS9aEWt7U6iutXXSS9zmWVxkJfgXvLEYVc@NPsCEIuc12VooiImyFPcjymiioZUXPLekSTlFS8KrVLPCSTKxAMKa69EzT1lm@cKX6AmfPX@HohIGjFXyoB2iliYQ64BhoO7ZkMAaEs28mYYhxvS2HawOKjSus9wXbNQljDzAZCzNV1Z5bDIheAMC8i9PmLowH9j9JF01NttWW8o204xnGOd5WvucmPODzBckwSB170G9MDFVsVsvoe0NTPh66OFq/qnNtiWNjvFVlQ25cT3Ty8swLmti3yeigRFI7IzDMzcy1q69uOQzQr5e0AWFlKegs2AeWcBYNbXlQCb1kJEbrmBcWsaluatU2e9TqDAH/MSsOGeZruyObfpE497sSAzW4hKbf5OF6c4rj9IC069/ZfDmZTctVbzAY/QM "Perl 5 – Try It Online"

#3: Post edited by

jhnc‭ · 2026-05-31T05:17:39Z (4 months ago)
invert for/map nesting to allows reusing each row read for both computations

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~~# [Perl 5], 124 bytes~~
Read stdin. Exits 1 if net, 0 if not.
```bash
~~perl -00ae'for$i(0..5){map/^.{$i}#/&&$b[$i]++,@F}@a=map{y/#//||()}@F;$m=@a>@b?@a:@b;@a=@b~~
if@a>@b;exit!grep$a[$_]>$m-2,0,-1'
```
When oriented with longer side vertical as shown in the challenge:
* nets have height 4 or 5
* nets never start or end with a "long" column (3+ for height 4; 4+ for height 5)
~~* non-nets of height 3 always start or end with a "long" column (2+)~~
* the squares may not be connected when the other orientation is chosen
* the height 6 non-net is just a single long column (6)
This simplifies to:
* non-nets have an end column containing more than height-2 squares
```
printf "%s\n" '...#..' '####..' '...#..' '......' '......' '......' |
# -00 slurps records in paragraph mode
# -a loops over records, with lines stored in @F
~~perl -00ne'~~
~~# array of non-zero counts of # in columns~~
~~for $i (0..5) {~~
~~map /^.{$i}#/ && $b[$i]++, @F~~
}
~~# array of non-zero counts of # in rows~~
~~@a = map{ y/#//||() } @F;~~
# get length of longer direction
$m = @a>@b ? @a : @b;
# use other direction for counts
@a = @b if @a>@b;
~~# test if either end count is out of range~~
# exit with the negation to save a character
exit ! grep $a[$_]>$m-2, 0,-1
'
echo $?
```
~~[Try it online!][TIO-mpsuqjx1]~~
[Perl 5]: https://www.perl.org/
[TIO-mpsuqjx1]: https://tio.run/##pVldTyJBEHznV@xRq0KEgbvEF4m6T/4J9Qwk6JGcQFhMziB//ThAPnZne7prOF7Wxdmhp7u6q7p3Opz9vlohmQ/zefKrPxsP87z2ng@T/H2QJxfDP6P5Ra@2vkk2fyaLZDobjecvSf0sT9q3yVn@OK63krzzmHc6r7NW0kifH7pPd/WPYV6/ro8n9WYvyQY3jWayXL1MZumo0XXuqrl46087P90iHS3ROT9PBw/p6OnyspXdL7P@zfqfi48OOp3Pz0Zzmd330rebrH@bDe6y/nU26K2XZIPa6GX7XW9j2LfX2XCa9h/S56fb9K39o9Vttb@vVnCbTw3rz@bydeekS83h67Z02T5XXeocjrvu7uRd9xtIm1cMgGSAMw1QjwXxl8VjlZ1lHGu/D0Lnqe5qe2D7Nbe0ZABAB3a3OVzAABSjjshdxSf8YzkwfrWXuhJADANwXKM7a7dBaSlUaG9jIG9XNACBbAocyzudAAU5U8rPe0ujkCU9EQosSLiASJgKpBAXLdlWL2MpaBMYEEEIIrc4ELLJzWRBAFIwbY2qr1oalo5u5FY5Wg5sfeXhwjAMFQKPDVVkwcrqQCUkMpZiQxebhgGAqdIBml/Bcqy8HeEBPQRlA@JzC7atOrLAp6G4Hfg0BIEB3lm6fCxnAVfgbQwcDbA49rDG5tgAtCWOFek4xLFwZIGHTa4yGyKCOBWxUayvjF93YQKpXWTJXYELihiIbkykEHjRcuG8UVVTNbBftjoWWVC6J5m3oMPFLIEysgzmhlUrAtDmSoYJQr/Aw7bV8SRfsgOErWLwgypDlTkwSCBUXYgexjHO8rgAVnJHQNtHuC51cVK7A6jQpsUTZYDdPVUqIbNriQYZse8LIxbauth3dtMvrrE8ED8fAFsytNw6KBFElmJVksH2vUxxHsNoaWjpVzphDsiioe3sfusowiw7qrKNxatWukLBV5ZqlG3oASph7KKp/HKo4VP1QKx8dNGaUMubSn2ltYtO8mWO5VVGhF/BO4tRxdz4E2wIfG6znRWjiAhbYQ@ySk0U1LKi55Z08acoMXjVahZ4SSZWIBhTXXqmaeussnCl@gJnz1/h6ISBoxW8rwdopYmIOuAYaDu2ZDAG@LNvJmGIcb0thysDio0rrPcF2zURYw8wGQszVdWeWwyIXgDAvIvT5i6MB/Y/SRdNTbZVlvKNtOMZxjneVr7nJjxQ5guSYRA79qDfmBiq2KyWwfeGpnw8dnG0flXn2hLHhniryIbcuJ7o5OWZFzSxb5PRUYnEdkZgmJuZaxdf3XIYoF8vaQPCwlLQWbAPLOEsGtryoBJ6yYiM1ikvLEJT3diqbfaoxRkC/mNW7DPMYbsTm36ROPe7EgM1uIim3@ThanOK0/SAtOvfyXQ@mozzVbvb7f8D "Perl 5 – Try It Online"

# [Perl 5], 118 bytes
Read stdin. Exits 1 if net, 0 if not.
```bash
perl -00ae'@a=map{for$i(0..5){/^.{$i}#/&&$b[$i]++}y/#//||()}@F;$m=@a>@b?@a:@b;@a=@b
if@a>@b;exit!grep$a[$_]>$m-2,0,-1'
```
When oriented with longer side vertical as shown in the challenge:
* nets have height 4 or 5
* nets never start or end with a "long" column (2+ for height 3; 3+ for height 4; 4+ for height 5) but non-nets always do
* for non-nets of height 3 the squares may not be connected when the other orientation is chosen
This simplifies to:
* non-nets have an start or end column containing more than height-2 squares
```
printf "%s\n" '...#..' '####..' '...#..' '......' '......' '......' |
# -00 slurps records in paragraph mode
# -a loops over records, with lines stored in @F
perl -00ae'
# array of non-zero counts in rows
@a = map {
# array of non-zero counts in columns
for $i (0..5) {
/^.{$i}#/ && $b[$i]++
}
y/#// || ()
} @F;
# get length of longer direction
$m = @a>@b ? @a : @b;
# use other direction for counts
@a = @b if @a>@b;
# test if start or end count is out of range
# exit with the negation to save a character
exit ! grep $a[$_]>$m-2, 0,-1
'
echo $?
```
[Try it online!][TIO-mptbi5b6]
[Perl 5]: https://www.perl.org/
[TIO-mptbi5b6]: https://tio.run/##pVldb9pQDH3nV2ScrAUVbtikvhS1zdP@RNtVINEOaQVEqLSK8tfHCuUjufG1z2V9SYMuxrGPfY6d2Wj@@3KNZDEqFsmvwXwyKorGazFKitdhkZyP/owX5/3Gx02y@TdZJrP5eLJ4Sppfi6R7k3wt7ifNTlJk90WWPc87SSt9vOs93DbfRkXzqjmZNtv9JB9et9rJap0Prl8Gs@XTdJ6OWz3nLtvL7KdbpuMVsrOzdHiXjh8uLlZvGbLs/b3VXuU/@unLdT64yYe3@eAqH/Y/TOTDxvhp@1l/49KX5/lolg7u0seHm/Sl@73T63S/rddwm78GPv42l887J10aDp@3lcv2e/WjzuFodXcnW90bkIzXHIDkgDMdUB8L4i@Lj1UNlvFYezsIPU/dqh2B7cfc0YoDAJ3YnXG4gAMoZx2RVsVv@I/lwMTVPuoqADEcwPGMHqydgcpRqNDe5kA2V3YAgWoKPJb3dAIU5Eqpft87GoUs6RuhxIKEC4iCqUEKcdmSffUqloI2gQERhCBqiwMhW9xMFQQgBdPXqP6qlWHl0Y3aqmbLge2vPFwYhqFS4LGhiixYVR3ohETFUmzoYsswADBVOkCLK1iOlc0REdBTUHUgvrZg@6ojC3wZiubAlyEIDPDB0uVjtQq4Bm9j4OiAxbGHMzbHBqAtcaxIxyGOhSMbPGxyldkQEcSpiI1yf2XiuksTSO0iS@4aXFDGQPRgIqXAy5YL142qmuqJ/fTVsciCMj3JvAUdLmYLlJFlMDesXhGANtcyTBD6DR62r44n@YofIHwVkx9UGarMgUECoe5CzDCOCZbHBbCKOwLaPsJ1qYuTxh1AhTYtnigH7Omp1gkZqxUaZMS@L4xYaOti39lDv3jGikD8fgBsy9Bq66BEENmKVUkGO/YyxXkMo5WhpV/pgjkgi4a2s@etowiz/KjLNhavWusKJV85qlG2oQeogrGbpvLLoYFP1QOx8tFFa0Ktbmr9ldYuOslXOZZXGRFxBR8sRhVz60@wKfC5zQ5WjCIifIW9yKoMUVDbil5b0sXfosTgVetZ4CWZ2IFgbHXpnaats6rClZoLnL1/haMLBo5W8L4eoJUmIvqAY6Dt2JbBOODvvpmCIdb1thyuLSg2obDeF2zPRKw9wFQszFJVZ24xIXoDAPMuTtu7MBHY/yTdNDXZVjvKD9KOZxjneF/5mZuIQJUvSIZB7NqDfmNiqGKzWwbfG5ry8TjF0fpV3WtLHBvirTIbcut6YpKXd17QxL5NRkclEjsZgWFuZq9dfnXLYYB@vaQtCEtHQVfBPrFEsGhoy4tK6C0jMlunvLAIbXVju7Y5o5Z3CPiPXbHPMAdzJw79InHurRILNbiIod/k4fpwitP0gGT173S2GE8nxbrb6w3@AQ "Perl 5 – Try It Online"

#2: Post edited by

jhnc‭ · 2026-05-30T21:23:23Z (4 months ago)
-a saves loading manually; reordering map saves a character

Copy Link

Raw

Markdown

~~# [Perl 5], 135 bytes~~
Read stdin. Exits 1 if net, 0 if not.
```bash
~~perl -00ne'@a=/\S+/g;for$i(0..5){map{$b[$i]++if/^.{$i}#/}@a}@a=map{y/#//||()}@a;$m=@a>@b?@a:@b;@a=@b~~
if@a>@b;exit!grep$a[$_]>$m-2,0,-1'
```
When oriented with longer side vertical as shown in the challenge:
* nets have height 4 or 5
* nets never start or end with a "long" column (3+ for height 4; 4+ for height 5)
* non-nets of height 3 always start or end with a "long" column (2+)
* the squares may not be connected when the other orientation is chosen
* the height 6 non-net is just a single long column (6)
This simplifies to:
* non-nets have an end column containing more than height-2 squares
```
printf "%s\n" '...#..' '####..' '...#..' '......' '......' '......' |
# -00 slurps records in paragraph mode
~~# -n loops over records~~
perl -00ne'
~~# array of the rows~~
~~@a = /\S+/g;~~
# array of non-zero counts of # in columns
for $i (0..5) {
~~map {~~
$b[$i]++ if /^.{$i}#/
~~} @a~~
}
# array of non-zero counts of # in rows
~~@a = map{ y/#//||() } @a;~~
# get length of longer direction
$m = @a>@b ? @a : @b;
# use other direction for counts
@a = @b if @a>@b;
# test if either end count is out of range
# exit with the negation to save a character
exit ! grep $a[$_]>$m-2, 0,-1
'
echo $?
```
~~[Try it online!][TIO-mpsswa6h]~~
[Perl 5]: https://www.perl.org/
[TIO-mpsswa6h]: https://tio.run/##pVnRbtpAEHznK1zGVUCBM62UlyAS/qGPSRqBBKmlBhAmUiOSXy8FAsFn7@3O0SiSY3I@9nZnd2bXi8ny99UGyWpSrJJfo@VsUhSNl2KSFC/jIrmY/MlXF/3G9ibZ/Zmsk8Uyn62mSfNrkXRvkq/F/azZSYrsvsiyp2UnaaWPd72H2@brpGheN2fzZrufDMeDVjt53wxHg@z@x2X21J/Ol2ne6jl31V4/jxbrdHyX5g@Xl/k0@@nWaf6O7H042v4Odv99zZBlb2@t9vaDfvo8GI5uhuPb4eh6OO5vlwzHjXy6/6y/s/HL03KySEd36ePDTfrc/d7pdbrfNhu43U8D25/d5ePOSZeGw8etd9k/V1/qHE67Hu7kXY8bSJvXDIBkgDMNUI8F8ZvFY/nOMo513Aeh89R3tT2w/5hb6hkA0IE9bA4XMADlqCNyV/GJ6rEcGL/aS50HEMMAnNbozjps4C2FCu19DOTtygYgkE2BY1VOJ0BBzhT/@crSKGRJT4QCCxIuIBKmBinERUu2tZKxFLQJDIggBJFbHAjZ5GayIAApmLZG1VctDb2jG7nlR8uBra88XBiGoUJQYUMVWbCyOlAJiYyl2NDFpmEAYKp0gOZXsBwrb0d4QA@Bb0B8bsG2VUcW@DQUtwOfhiAwwDtLl49@FnAF3sbAyQCLYz/X2BwbgLbEsSIdhzgWjizwsMlVZkNEEKciNsr1lfHrIUwgtYssuWtwQRkD0Y2JFIJKtFw4b1TVVA/sh62ORRaU7knmLehwMUugjCyDuWHVigC0uZJhgrBa4GHb6niS9@wAYasY/KDKUGUODBIIVReih3GMsypcACu5I6BdRbgudXFWuwOo0KbFE2WA3T3VKiGzq0eDjNivCiMW2rrYd3bTL66xPBA/HwBbMrTc@lQiiCzFqiSD7XuZ4ioMo6WhpV/phPlEFg1tZ/dbJxFm2VGXbSxetdIVCr6yVKNsQw9QCWMXTeWbQw2fqgdi5aOL1oRa3tTqK61ddJL3OZZXGRF@Be8sRhVz40@wIahym@2sGEVE2Ap7kOU1UVDLip5b0qU6RYnBq1azwEsysQLBmOrSM01bZ/nCleoLnD1/haMTBo5W8FU9QCtNRNQBx0DbsSWDMaA6@2YShhjX23K4NqDYucJ6X7BfEzH2AJOxMFNV7bnFgOgFAMy7OG3uwnjg@JV00dRkW20p30g7nmGc423le27CAz5fkAyD2LEH/cbEUMVmtQy@NzTl46mLo/WrOteWODbEW2U25Mb1RCcvz7ygiX2bjE5KJLYzAsPczFy7/OqWwwD9ekkbEJaWgs6CY2AJZ9HQlgeV0EtGZLTOeWERmurGVm2zRy3PEPAfs@Iqw3xud2bTLxLncVdioAYX0fSbPFxvTnGeHpB2/TtfrPL5rNh0e73ZPw "Perl 5 – Try It Online"

# [Perl 5], 124 bytes
Read stdin. Exits 1 if net, 0 if not.
```bash
perl -00ae'for$i(0..5){map/^.{$i}#/&&$b[$i]++,@F}@a=map{y/#//||()}@F;$m=@a>@b?@a:@b;@a=@b
if@a>@b;exit!grep$a[$_]>$m-2,0,-1'
```
When oriented with longer side vertical as shown in the challenge:
* nets have height 4 or 5
* nets never start or end with a "long" column (3+ for height 4; 4+ for height 5)
* non-nets of height 3 always start or end with a "long" column (2+)
* the squares may not be connected when the other orientation is chosen
* the height 6 non-net is just a single long column (6)
This simplifies to:
* non-nets have an end column containing more than height-2 squares
```
printf "%s\n" '...#..' '####..' '...#..' '......' '......' '......' |
# -00 slurps records in paragraph mode
# -a loops over records, with lines stored in @F
perl -00ne'
# array of non-zero counts of # in columns
for $i (0..5) {
map /^.{$i}#/ && $b[$i]++, @F
}
# array of non-zero counts of # in rows
@a = map{ y/#//||() } @F;
# get length of longer direction
$m = @a>@b ? @a : @b;
# use other direction for counts
@a = @b if @a>@b;
# test if either end count is out of range
# exit with the negation to save a character
exit ! grep $a[$_]>$m-2, 0,-1
'
echo $?
```
[Try it online!][TIO-mpsuqjx1]
[Perl 5]: https://www.perl.org/
[TIO-mpsuqjx1]: https://tio.run/##pVldTyJBEHznV@xRq0KEgbvEF4m6T/4J9Qwk6JGcQFhMziB//ThAPnZne7prOF7Wxdmhp7u6q7p3Opz9vlohmQ/zefKrPxsP87z2ng@T/H2QJxfDP6P5Ra@2vkk2fyaLZDobjecvSf0sT9q3yVn@OK63krzzmHc6r7NW0kifH7pPd/WPYV6/ro8n9WYvyQY3jWayXL1MZumo0XXuqrl46087P90iHS3ROT9PBw/p6OnyspXdL7P@zfqfi48OOp3Pz0Zzmd330rebrH@bDe6y/nU26K2XZIPa6GX7XW9j2LfX2XCa9h/S56fb9K39o9Vttb@vVnCbTw3rz@bydeekS83h67Z02T5XXeocjrvu7uRd9xtIm1cMgGSAMw1QjwXxl8VjlZ1lHGu/D0Lnqe5qe2D7Nbe0ZABAB3a3OVzAABSjjshdxSf8YzkwfrWXuhJADANwXKM7a7dBaSlUaG9jIG9XNACBbAocyzudAAU5U8rPe0ujkCU9EQosSLiASJgKpBAXLdlWL2MpaBMYEEEIIrc4ELLJzWRBAFIwbY2qr1oalo5u5FY5Wg5sfeXhwjAMFQKPDVVkwcrqQCUkMpZiQxebhgGAqdIBml/Bcqy8HeEBPQRlA@JzC7atOrLAp6G4Hfg0BIEB3lm6fCxnAVfgbQwcDbA49rDG5tgAtCWOFek4xLFwZIGHTa4yGyKCOBWxUayvjF93YQKpXWTJXYELihiIbkykEHjRcuG8UVVTNbBftjoWWVC6J5m3oMPFLIEysgzmhlUrAtDmSoYJQr/Aw7bV8SRfsgOErWLwgypDlTkwSCBUXYgexjHO8rgAVnJHQNtHuC51cVK7A6jQpsUTZYDdPVUqIbNriQYZse8LIxbauth3dtMvrrE8ED8fAFsytNw6KBFElmJVksH2vUxxHsNoaWjpVzphDsiioe3sfusowiw7qrKNxatWukLBV5ZqlG3oASph7KKp/HKo4VP1QKx8dNGaUMubSn2ltYtO8mWO5VVGhF/BO4tRxdz4E2wIfG6znRWjiAhbYQ@ySk0U1LKi55Z08acoMXjVahZ4SSZWIBhTXXqmaeussnCl@gJnz1/h6ISBoxW8rwdopYmIOuAYaDu2ZDAG@LNvJmGIcb0thysDio0rrPcF2zURYw8wGQszVdWeWwyIXgDAvIvT5i6MB/Y/SRdNTbZVlvKNtOMZxjneVr7nJjxQ5guSYRA79qDfmBiq2KyWwfeGpnw8dnG0flXn2hLHhniryIbcuJ7o5OWZFzSxb5PRUYnEdkZgmJuZaxdf3XIYoF8vaQPCwlLQWbAPLOEsGtryoBJ6yYiM1ikvLEJT3diqbfaoxRkC/mNW7DPMYbsTm36ROPe7EgM1uIim3@ThanOK0/SAtOvfyXQ@mozzVbvb7f8D "Perl 5 – Try It Online"

#1: Initial revision by

jhnc‭ · 2026-05-30T21:00:44Z (4 months ago)

Copy Link

Raw

Markdown

# [Perl 5], 135 bytes

Read stdin. Exits 1 if net, 0 if not.

```bash
perl -00ne'@a=/\S+/g;for$i(0..5){map{$b[$i]++if/^.{$i}#/}@a}@a=map{y/#//||()}@a;$m=@a>@b?@a:@b;@a=@b
if@a>@b;exit!grep$a[$_]>$m-2,0,-1'
```

When oriented with longer side vertical as shown in the challenge:
* nets have height 4 or 5
* nets never start or end with a "long" column (3+ for height 4; 4+ for height 5)
* non-nets of height 3 always start or end with a "long" column (2+)
  * the squares may not be connected when the other orientation is chosen
* the height 6 non-net is just a single long column (6)

This simplifies to:
* non-nets have an end column containing more than height-2 squares

```
printf "%s\n" '...#..' '####..' '...#..' '......' '......' '......' |

# -00 slurps records in paragraph mode
# -n loops over records
perl -00ne'
    # array of the rows
    @a = /\S+/g;

    # array of non-zero counts of # in columns
    for $i (0..5) {
        map {
            $b[$i]++ if /^.{$i}#/
        } @a
    }

    # array of non-zero counts of # in rows
    @a = map{ y/#//||() } @a;

    # get length of longer direction
    $m = @a>@b ? @a : @b;

    # use other direction for counts
    @a = @b if @a>@b;

    # test if either end count is out of range
    # exit with the negation to save a character
    exit ! grep $a[$_]>$m-2, 0,-1
'

echo $?
```


[Try it online!][TIO-mpsswa6h]

[Perl 5]: https://www.perl.org/
[TIO-mpsswa6h]: https://tio.run/##pVnRbtpAEHznK1zGVUCBM62UlyAS/qGPSRqBBKmlBhAmUiOSXy8FAsFn7@3O0SiSY3I@9nZnd2bXi8ny99UGyWpSrJJfo@VsUhSNl2KSFC/jIrmY/MlXF/3G9ibZ/Zmsk8Uyn62mSfNrkXRvkq/F/azZSYrsvsiyp2UnaaWPd72H2@brpGheN2fzZrufDMeDVjt53wxHg@z@x2X21J/Ol2ne6jl31V4/jxbrdHyX5g@Xl/k0@@nWaf6O7H042v4Odv99zZBlb2@t9vaDfvo8GI5uhuPb4eh6OO5vlwzHjXy6/6y/s/HL03KySEd36ePDTfrc/d7pdbrfNhu43U8D25/d5ePOSZeGw8etd9k/V1/qHE67Hu7kXY8bSJvXDIBkgDMNUI8F8ZvFY/nOMo513Aeh89R3tT2w/5hb6hkA0IE9bA4XMADlqCNyV/GJ6rEcGL/aS50HEMMAnNbozjps4C2FCu19DOTtygYgkE2BY1VOJ0BBzhT/@crSKGRJT4QCCxIuIBKmBinERUu2tZKxFLQJDIggBJFbHAjZ5GayIAApmLZG1VctDb2jG7nlR8uBra88XBiGoUJQYUMVWbCyOlAJiYyl2NDFpmEAYKp0gOZXsBwrb0d4QA@Bb0B8bsG2VUcW@DQUtwOfhiAwwDtLl49@FnAF3sbAyQCLYz/X2BwbgLbEsSIdhzgWjizwsMlVZkNEEKciNsr1lfHrIUwgtYssuWtwQRkD0Y2JFIJKtFw4b1TVVA/sh62ORRaU7knmLehwMUugjCyDuWHVigC0uZJhgrBa4GHb6niS9@wAYasY/KDKUGUODBIIVReih3GMsypcACu5I6BdRbgudXFWuwOo0KbFE2WA3T3VKiGzq0eDjNivCiMW2rrYd3bTL66xPBA/HwBbMrTc@lQiiCzFqiSD7XuZ4ioMo6WhpV/phPlEFg1tZ/dbJxFm2VGXbSxetdIVCr6yVKNsQw9QCWMXTeWbQw2fqgdi5aOL1oRa3tTqK61ddJL3OZZXGRF@Be8sRhVz40@wIahym@2sGEVE2Ap7kOU1UVDLip5b0qU6RYnBq1azwEsysQLBmOrSM01bZ/nCleoLnD1/haMTBo5W8FU9QCtNRNQBx0DbsSWDMaA6@2YShhjX23K4NqDYucJ6X7BfEzH2AJOxMFNV7bnFgOgFAMy7OG3uwnjg@JV00dRkW20p30g7nmGc423le27CAz5fkAyD2LEH/cbEUMVmtQy@NzTl46mLo/WrOteWODbEW2U25Mb1RCcvz7ygiX2bjE5KJLYzAsPczFy7/OqWwwD9ekkbEJaWgs6CY2AJZ9HQlgeV0EtGZLTOeWERmurGVm2zRy3PEPAfs@Iqw3xud2bTLxLncVdioAYX0fSbPFxvTnGeHpB2/TtfrPL5rNh0e73ZPw "Perl 5 – Try It Online"

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