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AWK, 145 bytes Pass 64 character string of 1s and 0s on stdin. Zero exit means success; non-zero means failure. awk 'function n(i){i<1||i>72||c-$i||($i=2)+n(i+9)+n(i+1)+n(i-9)+n(i-1)}{gsub...

posted 6mo ago by jhnc‭ · edited 6mo ago by jhnc‭

Answer

#4: Post edited by

jhnc‭ · 2026-03-31T14:01:30Z (6 months ago)
quick fix for horizontal wrapping

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~~**This code is broken (Fails: "The grid does not wrap toroidally")**~~
~~<s>~~
~~# AWK, 127 bytes~~
Pass 64 character string of 1s and 0s on stdin.
Zero exit means success; non-zero means failure.
```
~~awk 'function n(i){i<1||i>64||c-$i||($i=2)+n(i+8)+n(i+1)+n(i-8)+n(i-1)}{n(index($0,0));c=1;n(index($0,1));exit/[01]/}' FS= OFS=~~
```
Comments:
```
awk '
function n(i){
~~i<1||i>64 || # out of bounds?~~
c-$i || # incorrect value?
($i=2)+\
~~n(i+8)+n(i+1)+n(i-8)+n(i-1) # mark(replace) then recurse~~
}
{
n(index($0,0)); # find connected 0s
c=1; n(index($0,1)); # find connected 1s
exit /[01]/ # zero iff no 0s or 1s left
}
' FS= OFS=
```
* Same basic logic as my Perl answer
* `FS=` (non-standard but widely implemented) splits line into fields containing individual characters
* `OFS=` - assigning to a field cause line to be rewritten with fields separated by `OFS`; clearing it means result is unchanged (affects `index`)
~~[Try it online!][TIO-mmgi6y0b]~~
[TIO-mmgi6y0b]: https://tio.run/##rVJRS8MwEH7Przi6Ci1rWU5ExNoJgoov@rBHESldikFJpclw0PS317Td2o1WsNaEcLnLx3ff3SX6ei9nkKQZKCYVvEWZYFKSHD4zLlQC1okEfwmWBzaFgpCb2/uHxxzuVuGTOa9QlMlGxIqnAoTD3ZxfodZ8eX6mdezbXGvH5uGpOzeP84vGYG38xvPRLXJC4pAGAANCiMGINds6NvWo6wZxiMFBCE2IkBnbcgWLZ4ovC1IL3zlwDVYSfUhmwSVYKtuYy0AWr6kWuJCKRWtIE6gYSVGWdOIyeau0BCeuPc9EOVN58H95sOpPPaCOqKp2yI5s9GhFXaMbQV3v948dqB8ZnNhRZfhHQ3uKWsLGwxqJx7uNt7j@H6pBiPQX@4Dux1bjblRj9DSFfQM "AWK – Try It Online"
~~</s>~~

# AWK, 145 bytes
Pass 64 character string of 1s and 0s on stdin.
Zero exit means success; non-zero means failure.
```
awk 'function n(i){i<1||i>72||c-$i||($i=2)+n(i+9)+n(i+1)+n(i-9)+n(i-1)}{gsub(/.{8}/,"&2");n(index($0,0));c=1;n(index($0,1));exit/[01]/}' FS= OFS=
```
Comments:
```
awk '
function n(i){
i<1||i>72 || # out of bounds?
c-$i || # incorrect value?
($i=2)+\
n(i+9)+n(i+1)+n(i-9)+n(i-1) # mark(replace) then recurse
}
{
gsub(/.{8}/,"&2"); # add sentinels to detect horizontal wrap
n(index($0,0)); # find connected 0s
c=1; n(index($0,1)); # find connected 1s
exit /[01]/ # zero iff no 0s or 1s left
}
' FS= OFS=
```
* Same basic logic as my Perl answer
* `FS=` (non-standard but widely implemented) splits line into fields containing individual characters
* `OFS=` - assigning to a field cause line to be rewritten with fields separated by `OFS`; clearing it means result is unchanged (affects `index`)
[Try it online!][TIO-mneompza]
[AWK]: https://www.gnu.org/software/gawk/manual/gawk.html
[TIO-mneompza]: https://tio.run/##rVJNT4QwEL33V0y6aCAL0uHiB7ImJmq86MGjMQZZ0EbTNbQbNwF@O/KxwG5Asyu2IcNMX99M34z/9Z5PIFrEoEKp4M2PRSglSeAz5kJFQA8kWDOgJmgMMkIur25u7xK4fvDui@8ZsjxaikDxhQChcyPh55imfHbspGlgaTxNdY17jjEtDqentcHKWLVnoZElhAQecwEGCiGvcvmi20fJSWab9NChhkuKa2IernSNmcww3MBDdyOERYiQSbjiCuxHhk82qd6yduACaOR/yJDCGVAVL4ufgcRmLQBwIVXoz2ERQclIsjxnI1eRt0xLcORqeEaWM5YH/5cHS32qBnVE5WuH7J5C711RJ3RdUKd9c9iB@pHBjm29DP9oWK@ilrD2sELi9m7jLa4/QxUIke2wN@h@lBrXrdqnnkahhmXXxm3j@0PUwoYn6pchqom@AQ "AWK – Try It Online"

#3: Post edited by

jhnc‭ · 2026-03-31T13:06:39Z (6 months ago)
placeholder comment until code fixed

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# AWK, 127 bytes
Pass 64 character string of 1s and 0s on stdin.
Zero exit means success; non-zero means failure.
```
awk 'function n(i){i<1||i>64||c-$i||($i=2)+n(i+8)+n(i+1)+n(i-8)+n(i-1)}{n(index($0,0));c=1;n(index($0,1));exit/[01]/}' FS= OFS=
```
Comments:
```
awk '
function n(i){
i<1||i>64 || # out of bounds?
c-$i || # incorrect value?
($i=2)+\
n(i+8)+n(i+1)+n(i-8)+n(i-1) # mark(replace) then recurse
}
{
n(index($0,0)); # find connected 0s
c=1; n(index($0,1)); # find connected 1s
exit /[01]/ # zero iff no 0s or 1s left
}
' FS= OFS=
```
* Same basic logic as my Perl answer
* `FS=` (non-standard but widely implemented) splits line into fields containing individual characters
* `OFS=` - assigning to a field cause line to be rewritten with fields separated by `OFS`; clearing it means result is unchanged (affects `index`)
[Try it online!][TIO-mmgi6y0b]
[TIO-mmgi6y0b]: https://tio.run/##rVJRS8MwEH7Przi6Ci1rWU5ExNoJgoov@rBHESldikFJpclw0PS317Td2o1WsNaEcLnLx3ff3SX6ei9nkKQZKCYVvEWZYFKSHD4zLlQC1okEfwmWBzaFgpCb2/uHxxzuVuGTOa9QlMlGxIqnAoTD3ZxfodZ8eX6mdezbXGvH5uGpOzeP84vGYG38xvPRLXJC4pAGAANCiMGINds6NvWo6wZxiMFBCE2IkBnbcgWLZ4ovC1IL3zlwDVYSfUhmwSVYKtuYy0AWr6kWuJCKRWtIE6gYSVGWdOIyeau0BCeuPc9EOVN58H95sOpPPaCOqKp2yI5s9GhFXaMbQV3v948dqB8ZnNhRZfhHQ3uKWsLGwxqJx7uNt7j@H6pBiPQX@4Dux1bjblRj9DSFfQM "AWK – Try It Online"

**This code is broken (Fails: "The grid does not wrap toroidally")**
<s>
# AWK, 127 bytes
Pass 64 character string of 1s and 0s on stdin.
Zero exit means success; non-zero means failure.
```
awk 'function n(i){i<1||i>64||c-$i||($i=2)+n(i+8)+n(i+1)+n(i-8)+n(i-1)}{n(index($0,0));c=1;n(index($0,1));exit/[01]/}' FS= OFS=
```
Comments:
```
awk '
function n(i){
i<1||i>64 || # out of bounds?
c-$i || # incorrect value?
($i=2)+\
n(i+8)+n(i+1)+n(i-8)+n(i-1) # mark(replace) then recurse
}
{
n(index($0,0)); # find connected 0s
c=1; n(index($0,1)); # find connected 1s
exit /[01]/ # zero iff no 0s or 1s left
}
' FS= OFS=
```
* Same basic logic as my Perl answer
* `FS=` (non-standard but widely implemented) splits line into fields containing individual characters
* `OFS=` - assigning to a field cause line to be rewritten with fields separated by `OFS`; clearing it means result is unchanged (affects `index`)
[Try it online!][TIO-mmgi6y0b]
[TIO-mmgi6y0b]: https://tio.run/##rVJRS8MwEH7Przi6Ci1rWU5ExNoJgoov@rBHESldikFJpclw0PS317Td2o1WsNaEcLnLx3ff3SX6ei9nkKQZKCYVvEWZYFKSHD4zLlQC1okEfwmWBzaFgpCb2/uHxxzuVuGTOa9QlMlGxIqnAoTD3ZxfodZ8eX6mdezbXGvH5uGpOzeP84vGYG38xvPRLXJC4pAGAANCiMGINds6NvWo6wZxiMFBCE2IkBnbcgWLZ4ovC1IL3zlwDVYSfUhmwSVYKtuYy0AWr6kWuJCKRWtIE6gYSVGWdOIyeau0BCeuPc9EOVN58H95sOpPPaCOqKp2yI5s9GhFXaMbQV3v948dqB8ZnNhRZfhHQ3uKWsLGwxqJx7uNt7j@H6pBiPQX@4Dux1bjblRj9DSFfQM "AWK – Try It Online"
</s>

#2: Post edited by

jhnc‭ · 2026-03-07T15:56:05Z (6 months ago)
link to TIO

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~~# awk, 127 bytes~~
Pass 64 character string of 1s and 0s on stdin.
Zero exit means success; non-zero means failure.
```
awk 'function n(i){i<1||i>64||c-$i||($i=2)+n(i+8)+n(i+1)+n(i-8)+n(i-1)}{n(index($0,0));c=1;n(index($0,1));exit/[01]/}' FS= OFS=
```
Comments:
```
awk '
function n(i){
i<1||i>64 || # out of bounds?
c-$i || # incorrect value?
($i=2)+\
n(i+8)+n(i+1)+n(i-8)+n(i-1) # mark(replace) then recurse
}
{
n(index($0,0)); # find connected 0s
c=1; n(index($0,1)); # find connected 1s
exit /[01]/ # zero iff no 0s or 1s left
}
' FS= OFS=
```
* Same basic logic as my Perl answer
* `FS=` (non-standard but widely implemented) splits line into fields containing individual characters
* `OFS=` - assigning to a field cause line to be rewritten with fields separated by `OFS`; clearing it means result is unchanged (affects `index`)

# AWK, 127 bytes
Pass 64 character string of 1s and 0s on stdin.
Zero exit means success; non-zero means failure.
```
awk 'function n(i){i<1||i>64||c-$i||($i=2)+n(i+8)+n(i+1)+n(i-8)+n(i-1)}{n(index($0,0));c=1;n(index($0,1));exit/[01]/}' FS= OFS=
```
Comments:
```
awk '
function n(i){
i<1||i>64 || # out of bounds?
c-$i || # incorrect value?
($i=2)+\
n(i+8)+n(i+1)+n(i-8)+n(i-1) # mark(replace) then recurse
}
{
n(index($0,0)); # find connected 0s
c=1; n(index($0,1)); # find connected 1s
exit /[01]/ # zero iff no 0s or 1s left
}
' FS= OFS=
```
* Same basic logic as my Perl answer
* `FS=` (non-standard but widely implemented) splits line into fields containing individual characters
* `OFS=` - assigning to a field cause line to be rewritten with fields separated by `OFS`; clearing it means result is unchanged (affects `index`)
[Try it online!][TIO-mmgi6y0b]
[TIO-mmgi6y0b]: https://tio.run/##rVJRS8MwEH7Przi6Ci1rWU5ExNoJgoov@rBHESldikFJpclw0PS317Td2o1WsNaEcLnLx3ff3SX6ei9nkKQZKCYVvEWZYFKSHD4zLlQC1okEfwmWBzaFgpCb2/uHxxzuVuGTOa9QlMlGxIqnAoTD3ZxfodZ8eX6mdezbXGvH5uGpOzeP84vGYG38xvPRLXJC4pAGAANCiMGINds6NvWo6wZxiMFBCE2IkBnbcgWLZ4ovC1IL3zlwDVYSfUhmwSVYKtuYy0AWr6kWuJCKRWtIE6gYSVGWdOIyeau0BCeuPc9EOVN58H95sOpPPaCOqKp2yI5s9GhFXaMbQV3v948dqB8ZnNhRZfhHQ3uKWsLGwxqJx7uNt7j@H6pBiPQX@4Dux1bjblRj9DSFfQM "AWK – Try It Online"

#1: Initial revision by

jhnc‭ · 2026-03-07T15:46:54Z (6 months ago)

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# awk, 127 bytes

Pass 64 character string of 1s and 0s on stdin.

Zero exit means success; non-zero means failure.

```
awk 'function n(i){i<1||i>64||c-$i||($i=2)+n(i+8)+n(i+1)+n(i-8)+n(i-1)}{n(index($0,0));c=1;n(index($0,1));exit/[01]/}' FS= OFS=
```

Comments:

```
awk '
    function n(i){
        i<1||i>64 ||  # out of bounds?
        c-$i ||       # incorrect value?
        ($i=2)+\
        n(i+8)+n(i+1)+n(i-8)+n(i-1)  # mark(replace) then recurse
    }
    {
             n(index($0,0));  # find connected 0s
        c=1; n(index($0,1));  # find connected 1s

        exit /[01]/  # zero iff no 0s or 1s left
    }
' FS= OFS=
```

* Same basic logic as my Perl answer
* `FS=` (non-standard but widely implemented) splits line into fields containing individual characters
* `OFS=` - assigning to a field cause line to be rewritten with fields separated by `OFS`; clearing it means result is unchanged (affects `index`)

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