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#6: Post edited by

jhnc‭ · 2026-05-26T05:31:16Z (4 months ago)
shorter success check

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~~# [Perl 5], 235 bytes~~
Brute-force check.
Reads line of space-separated digits from stdin. Prints answer to stdout.
If empty output is permitted as "impossible", omit final `say` to save 10 bytes.
```none
perl -aE'map{@o=/./g;for$f("15(26(374))","15((263)74)","(15(263))74","(152)6(374)","((152)63)74"){map{$_=sprintf $f=~s/\d/%$&\$s/gr,@F[@o],/./g;if(24eq eval){say;exit}}glob"{+,-,\\*,/}"x 3}}grep!/(.).*\1/,glob"{0,1,2,3}"x 4;say"false"'
```
```bash
~~perl -aE '~~
~~# 0. four numbers have been loaded into @F by -a option~~
# 2. loop over each permutation of offsets
map {
~~@o = /./g; # temp var since $_ is reused in nested map~~
# 3. loop over the five ways to group operations
~~# $f is a compacted format string for sprintf~~
for $f (
"15(26(374))",
"15((263)74)",
"(15(263))74",
"(152)6(374)",
"((152)63)74"
){
# 5. loop over each operator combination
~~map{~~
# 6. expand the format string
# substitute in the numbers and operators
~~# save resulting expression as $_~~
$_ =
sprintf
$f =~ s/\d/%$&\$s/gr,
@F[@o], /./g
;
# 7. execute the expression
# if result is 24, print expression and exit
if (24 eq eval) {
~~say;~~
~~exit~~
}
# 4. generate all combinations of three operators
} glob "{+,-,\\*,/}" x 3
}
# 1. generate all permutations of the offsets into @F
} grep !/(.).*\1/, glob "{0,1,2,3}" x 4;
# 8. if we get here, no solution was found
say "false"
'
```
~~[Try it online!][TIO-mpkf6ntj]~~
[Perl 5]: https://www.perl.org/
[TIO-mpkf6ntj]: https://tio.run/##ZZDRbpswFIbv/RSeSyu7MXHwAQxCVLmKtGcoVUU6kyKRwDCZmKL00cdsmCY1ta/@z/855z/udN9E09loXOlyOPcaE1P@JhlC2x3Osbd73rzkH2ItDhl6e2@PXYa6vj4NFSb3vtwYnD9hwr3XDJnzHlf4Mh3L7rJt87mkanuvoiSIqIwpqJAxwp2yEpiVVtH5EZiVi5JssTq1SGcl7OIae6@5@Tffq/IPI4of4t57KDwjDj3f7p637QufR9cVlaH@ifWvsmEXu5Nd6Q7bQHjQZsDvZX/SxqBe26VP@A7rsR4Qul4PTbsnlxX3eVE8cnElIwZLe919E3TN1o9FIPhi2vCASw7OEmbu16qyMZpMV/RQZRNApLD/hIHCGPmKoQDC2IFY0MAHETIEoGaLorACoRxIEgcSQcFPBNiiIJiLvh@71ph632iLVHqLomXWJ6S@ILkgqkblB0xIFMRx8j9SLBKGoiidm0c2cypSJGUYOi2pHMOVzSztuelrN01uURjfTldJmn4pBJi/aLTXhz9tN9TtyUx@@Rc "Perl 5 – Try It Online"

# [Perl 5], 228 bytes
Brute-force check.
Reads line of space-separated digits from stdin. Prints answer to stdout.
If empty output is permitted as "impossible", omit final `say` to save 10 bytes.
```none
perl -aE'map{@o=/./g;for$f("15(26(374))","15((263)74)","(15(263))74","(152)6(374)","((152)63)74"){map{$_=sprintf$f=~s/\d/%$&\$s/gr,@F[@o],/./g;24-eval||exit!say}glob"{+,-,\\*,/}"x 3}}grep!/(.).*\1/,glob"{0,1,2,3}"x 4;say"false"'
```
```bash
echo 1 2 3 4 | perl -aE '
# 0. the four numbers are loaded into @F by -a option
# 2. loop over each permutation of offsets
map {
@o = /./g; # temp var as $_ is overwritten in inner map
# 3. loop over the five ways to group operations
# $f is a compressed format string for sprintf
for $f (
"15(26(374))",
"15((263)74)",
"(15(263))74",
"(152)6(374)",
"((152)63)74"
){
# 5. loop over each operator combination
map {
# 6. expand the format string
# substitute in the numbers and operators
# save resulting expression as $_ (for eval/say)
$_ =
sprintf
$f =~ s/\d/%$&\$s/gr,
@F[@o], /./g
;
# 7. execute the expression
# if result is 24, print expression and exit
24-eval || exit !say
# 4. generate all combinations of three operators
} glob "{+,-,\\*,/}" x 3
}
# 1. generate all permutations of the offsets into @F
} grep !/(.).*\1/, glob "{0,1,2,3}" x 4;
# 8. if we get here, no solution was found
say "false"
'
```
[Try it online!][TIO-mpm6o7le]
[Perl 5]: https://www.perl.org/
[TIO-mpm6o7le]: https://tio.run/##ZZDRbpswFIbv/RQuo6vd2HGwAcMQUS66SLvZHqBUFdkMjUQCwmRiovTRl9kwTRo1N/4/zvnP79OotgquF61gofLu0iro6PyXkwDwAXZKd/Alb89Ka7DbwxS6@8fNU/rG1qxMwPeX@tQkoGmP566Azi3lGw3TLXSI@5wAa6kvBw3vVH/s7hJgBLRXOMCy7mr48O3rZzhOeLie8mbY1elkXNStWyDHCxAPkZA@xg6xykiBjTQKTT8FNnJWHM@lVs3Sljp4sMbuc6r/pnSL9E2z7Ae7dT9mrmZlS3b7x139RKbR3KfqZ169vtqgN2YRY1nVB2dYEUqy7J6w0emhGMeyVc0NQ2u8vs88RuaiDfEIJ8KW@IldYpFXWjnXxSJHukU4Afb5n65CBBLSLRRI9AGVGHjCDy0IGfKoYD4GQsipRCKxEkxaEEUWRAwJGjFhmjxvavpyamqtj4dKGSTjJQrmWf8h@Q7xGSHZS@phxoEXhtG/SCGLMAiCeDIPTOaYxYBz37eaI977K5OZm7PwNS@NlsgPl9NlFMfvGoWYVtSbj4rfddMd67O@0vwP "Perl 5 – Try It Online"

#5: Post edited by

jhnc‭ · 2026-05-24T23:59:59Z (4 months ago)
less efficient but much shorter permutation generation

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~~# [Perl 5], 327 bytes~~
Brute-force check.
Reads line of space-separated digits from stdin. Prints answer to stdout.
If empty output is permitted as "impossible", omit final `say` to save 10 bytes.
```none
perl -aE'@o=0..3;for(;;){for$f("15(26(374))","15((263)74)","(15(263))74","(152)6(374)","((152)63)74"){map{$_=sprintf$f=~s/\d/%$&\$s/gr,@F[@o],/./g;if(24eq eval){say;exit}}glob"{+,-,\\*,/}"x 3}$i=$#o;--$i while$o[$i-1]>$o[$i];$j=$i or last;push@o,reverse splice@o,$i;++$j while$o[$i-1]>$o[$j];@o[$i-1,$j]=@o[$j,$i-1]}say"false"'
```
```bash
~~perl -aE'~~
# Fischer-Krause ordered permutation generator (cf. perlfaq4)
~~# 0. four numbers have been loaded into @F~~
# initialise list of offsets into @F that will be permuted
~~@o = 0..3;~~
~~# 1. loop over each permutation~~
~~for (;;) {~~
# 2. loop over the five ways to group operations
# $f is a compacted format string for sprintf
for $f (
"15(26(374))",
"15((263)74)",
"(15(263))74",
"(152)6(374)",
"((152)63)74"
){
~~# 4. loop over each operator combination~~
~~map {~~
~~# 5. expand the format string~~
~~# substitute in the digits and operators~~
# save resulting expression as $_
$_ =
sprintf
$f =~ s/\d/%$&\$s/gr,
@F[@o], /./g
;
~~# 6. execute the expression~~
# if result is 24, print expression and exit
if (24 eq eval) {
say;
exit
}
~~# 3. generate all combinations of three operators~~
} glob "{+,-,\\*,/}" x 3
}
# 7. permute the offsets
~~$i = $#o;~~
~~--$i while $o[$i-1]>$o[$i];~~
~~$j = $i or last;~~
~~push @o, reverse splice @o, $i;~~
~~++$j while $o[$i-1]>$o[$j];~~
~~@o[$i-1,$j] = @o[$j,$i-1]~~
}
# 8. if we get here, no solution was found
say "false"
```
~~[Try it online!][TIO-mpke96xq]~~
[Perl 5]: https://www.perl.org/
[TIO-mpke96xq]: https://tio.run/##bZFdb5swFIbv/Sssx63sBccB8ymLiKtK@w1JVJHOJI5IYJh0TIj@9KUGpElLBxec9zkffo@pVVMG95tRsFB5e2sURCb/jSQA2QtMIX7ZrvfpB1/xowRvp@pSS1A3@toWED0xb21guoHIwa8SmNsBFrC/Z1W6Xq2ELKqGSEl7@8UFQW5AvJCIyKcUOaOyUlArrSJTUlArZ@XRuRQ5AJFZj7WI9pe87vFramYTuEg/DN/94E/4eYcNPzZO9rLNqr0zOdYF8Xz1E6r3vKS93cuutYCq0y1olF32ChfQ2oOtMi085c1VGQPAMBzL6oD6pcOc3e6bwwfUQTFgneJFJQFjWMNfJ10qXG2xZu5@MwV7ic@pTdl5ZW5aWd/MKaucRr2rxl6vqUv9pizAWi6X@PyfEee9zGbt2Dgd47MzpYfxnxR5aRS6D@C5kHchggiyDRREdAGLKHCFH44g5MRlgvsUCBFNJRERS8GjEcTxCGJOBIu5sE2uOzV9v9SVMfpQKoui5BEF81n/oOgL8mZEoi5iLuUecMMw/msp5DEFQZBMwwPrOeEJ8DzfH7VHvM5fWs@efR7m2k3jR@SHj6dHcZJ8aRRiuqLOvkz8qepWV1dzZ/kn "Perl 5 – Try It Online"

# [Perl 5], 235 bytes
Brute-force check.
Reads line of space-separated digits from stdin. Prints answer to stdout.
If empty output is permitted as "impossible", omit final `say` to save 10 bytes.
```none
perl -aE'map{@o=/./g;for$f("15(26(374))","15((263)74)","(15(263))74","(152)6(374)","((152)63)74"){map{$_=sprintf $f=~s/\d/%$&\$s/gr,@F[@o],/./g;if(24eq eval){say;exit}}glob"{+,-,\\*,/}"x 3}}grep!/(.).*\1/,glob"{0,1,2,3}"x 4;say"false"'
```
```bash
perl -aE '
# 0. four numbers have been loaded into @F by -a option
# 2. loop over each permutation of offsets
map {
@o = /./g; # temp var since $_ is reused in nested map
# 3. loop over the five ways to group operations
# $f is a compacted format string for sprintf
for $f (
"15(26(374))",
"15((263)74)",
"(15(263))74",
"(152)6(374)",
"((152)63)74"
){
# 5. loop over each operator combination
map{
# 6. expand the format string
# substitute in the numbers and operators
# save resulting expression as $_
$_ =
sprintf
$f =~ s/\d/%$&\$s/gr,
@F[@o], /./g
;
# 7. execute the expression
# if result is 24, print expression and exit
if (24 eq eval) {
say;
exit
}
# 4. generate all combinations of three operators
} glob "{+,-,\\*,/}" x 3
}
# 1. generate all permutations of the offsets into @F
} grep !/(.).*\1/, glob "{0,1,2,3}" x 4;
# 8. if we get here, no solution was found
say "false"
'
```
[Try it online!][TIO-mpkf6ntj]
[Perl 5]: https://www.perl.org/
[TIO-mpkf6ntj]: https://tio.run/##ZZDRbpswFIbv/RSeSyu7MXHwAQxCVLmKtGcoVUU6kyKRwDCZmKL00cdsmCY1ta/@z/855z/udN9E09loXOlyOPcaE1P@JhlC2x3Osbd73rzkH2ItDhl6e2@PXYa6vj4NFSb3vtwYnD9hwr3XDJnzHlf4Mh3L7rJt87mkanuvoiSIqIwpqJAxwp2yEpiVVtH5EZiVi5JssTq1SGcl7OIae6@5@Tffq/IPI4of4t57KDwjDj3f7p637QufR9cVlaH@ifWvsmEXu5Nd6Q7bQHjQZsDvZX/SxqBe26VP@A7rsR4Qul4PTbsnlxX3eVE8cnElIwZLe919E3TN1o9FIPhi2vCASw7OEmbu16qyMZpMV/RQZRNApLD/hIHCGPmKoQDC2IFY0MAHETIEoGaLorACoRxIEgcSQcFPBNiiIJiLvh@71ph632iLVHqLomXWJ6S@ILkgqkblB0xIFMRx8j9SLBKGoiidm0c2cypSJGUYOi2pHMOVzSztuelrN01uURjfTldJmn4pBJi/aLTXhz9tN9TtyUx@@Rc "Perl 5 – Try It Online"

#4: Post edited by

jhnc‭ · 2026-05-24T23:20:10Z (4 months ago)
alternate format string compaction scheme allows shorter expansion code

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~~# [Perl 5], 338 bytes~~
Brute-force check.
Reads line of space-separated digits from stdin. Prints answer to stdout.
```none
perl -aE'@o=0..3;for(;;){for$f("d5(d6(d7d))","d5((d6d)7d)","(d5(d6d))7d","(d5d)6(d7d)","((d5d)6d)7d"){map{$_=sprintf$f=~s/d/%d/gr=~s/\d/%$&\$s/gr,@F[@o],/./g;if(24eq eval){say;exit}}glob"{+,-,\\*,/}"x 3}$i=$#o;--$i while$o[$i-1]>$o[$i];$j=$i or last;push@o,reverse splice@o,$i;++$j while$o[$i-1]>$o[$j];@o[$i-1,$j]=@o[$j,$i-1]}say"false"'
```
```bash
perl -aE'
# Fischer-Krause ordered permutation generator (cf. perlfaq4)
# 0. four numbers have been loaded into @F
# initialise list of offsets into @F that will be permuted
@o = 0..3;
# 1. loop over each permutation
for (;;) {
~~# 2. loop over the 5 possible ways to group operations~~
# $f is a compacted format string for sprintf
for $f (
~~"d5(d6(d7d))",~~
~~"d5((d6d)7d)",~~
~~"(d5(d6d))7d",~~
~~"(d5d)6(d7d)",~~
~~"((d5d)6d)7d"~~
){
# 4. loop over each operator combination
map {
# 5. expand the format string
# substitute in the digits and operators
# save resulting expression as $_
$_ =
sprintf
$f =~ s/d/%d/gr
=~ s/\d/%$&\$s/gr,
@F[@o], /./g
;
~~# 6. execute the expression and test if if equals 24~~
~~# if it does, print it and exit~~
if (24 eq eval) {
say;
exit
}
# 3. generate all combinations of three operators
} glob "{+,-,\\*,/}" x 3
}
# 7. permute the offsets
$i = $#o;
--$i while $o[$i-1]>$o[$i];
$j = $i or last;
push @o, reverse splice @o, $i;
++$j while $o[$i-1]>$o[$j];
@o[$i-1,$j] = @o[$j,$i-1]
}
# 8. if we get here, no solution was found
say "false"
'
```
~~[Try it online!][TIO-mpkdcgsy]~~
[Perl 5]: https://www.perl.org/
[TIO-mpkdcgsy]: https://tio.run/##bZHfjqIwFMbv@xRN7UzKSq1QoJAGw5XJPoOaCQ5FMSgsxVk2hHn0dQskm6yzcMH5fudPv1Nq1ZT@464VzFXa3hsFkU5/IQlAsoUxxNvd@hB/shU7SfB@rq61BHVT3NocohfqrjWMNxDZ@E0CfT/CHPaPpIrXqxWXedUQKa3efHFOUOaTLCCZyCwL2aMyMrOMNIpMSZMR2awyay5FNkBk1mMtsvprWvf4LdazCZzHn5pl7CVjp2YM9ybGr3usjbaT7S6pDvZkvsiJ66kfUH2kpdWbFc2GC6i6ogWNMnvf4AIap7BVuoXntLkprQEYhlNZHVG/tKm933@z2YA6yAdcxHhRSUApLuDPc1EqXO1wQZ3DZgoOEl9ikzLzylS3sr7rc1LZjfpQjblpXZfFuzIAF3K5xJf/jLgcZDJr28TxGF/sKT2MvydPS63QYwCvuXxw7gtIN5AT3vlUWMDhXjCCgBGHcuZZgHMxlQjCl5yJEYThCEJGOA0ZN02OMzV9v9aV1sWxVAaJ6Bn581n/IPEFuTMiohPUsZgLnCAI/1oKWGgB34@m4b7xHLEIuK7njdolbuctjWfXPE9zzabhM/KC59NFGEVfGjmfrqgzL@W/q7otqpt@0PQP "Perl 5 – Try It Online"

# [Perl 5], 327 bytes
Brute-force check.
Reads line of space-separated digits from stdin. Prints answer to stdout.
If empty output is permitted as "impossible", omit final `say` to save 10 bytes.
```none
perl -aE'@o=0..3;for(;;){for$f("15(26(374))","15((263)74)","(15(263))74","(152)6(374)","((152)63)74"){map{$_=sprintf$f=~s/\d/%$&\$s/gr,@F[@o],/./g;if(24eq eval){say;exit}}glob"{+,-,\\*,/}"x 3}$i=$#o;--$i while$o[$i-1]>$o[$i];$j=$i or last;push@o,reverse splice@o,$i;++$j while$o[$i-1]>$o[$j];@o[$i-1,$j]=@o[$j,$i-1]}say"false"'
```
```bash
perl -aE'
# Fischer-Krause ordered permutation generator (cf. perlfaq4)
# 0. four numbers have been loaded into @F
# initialise list of offsets into @F that will be permuted
@o = 0..3;
# 1. loop over each permutation
for (;;) {
# 2. loop over the five ways to group operations
# $f is a compacted format string for sprintf
for $f (
"15(26(374))",
"15((263)74)",
"(15(263))74",
"(152)6(374)",
"((152)63)74"
){
# 4. loop over each operator combination
map {
# 5. expand the format string
# substitute in the digits and operators
# save resulting expression as $_
$_ =
sprintf
$f =~ s/\d/%$&\$s/gr,
@F[@o], /./g
;
# 6. execute the expression
# if result is 24, print expression and exit
if (24 eq eval) {
say;
exit
}
# 3. generate all combinations of three operators
} glob "{+,-,\\*,/}" x 3
}
# 7. permute the offsets
$i = $#o;
--$i while $o[$i-1]>$o[$i];
$j = $i or last;
push @o, reverse splice @o, $i;
++$j while $o[$i-1]>$o[$j];
@o[$i-1,$j] = @o[$j,$i-1]
}
# 8. if we get here, no solution was found
say "false"
```
[Try it online!][TIO-mpke96xq]
[Perl 5]: https://www.perl.org/
[TIO-mpke96xq]: https://tio.run/##bZFdb5swFIbv/Sssx63sBccB8ymLiKtK@w1JVJHOJI5IYJh0TIj@9KUGpElLBxec9zkffo@pVVMG95tRsFB5e2sURCb/jSQA2QtMIX7ZrvfpB1/xowRvp@pSS1A3@toWED0xb21guoHIwa8SmNsBFrC/Z1W6Xq2ELKqGSEl7@8UFQW5AvJCIyKcUOaOyUlArrSJTUlArZ@XRuRQ5AJFZj7WI9pe87vFramYTuEg/DN/94E/4eYcNPzZO9rLNqr0zOdYF8Xz1E6r3vKS93cuutYCq0y1olF32ChfQ2oOtMi085c1VGQPAMBzL6oD6pcOc3e6bwwfUQTFgneJFJQFjWMNfJ10qXG2xZu5@MwV7ic@pTdl5ZW5aWd/MKaucRr2rxl6vqUv9pizAWi6X@PyfEee9zGbt2Dgd47MzpYfxnxR5aRS6D@C5kHchggiyDRREdAGLKHCFH44g5MRlgvsUCBFNJRERS8GjEcTxCGJOBIu5sE2uOzV9v9SVMfpQKoui5BEF81n/oOgL8mZEoi5iLuUecMMw/msp5DEFQZBMwwPrOeEJ8DzfH7VHvM5fWs@efR7m2k3jR@SHj6dHcZJ8aRRiuqLOvkz8qepWV1dzZ/kn "Perl 5 – Try It Online"

#3: Post edited by

jhnc‭ · 2026-05-24T22:52:15Z (4 months ago)
no point allowing for arbitrary length of @F when code assumes exactly 4 elements

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~~# [Perl 5], 340 bytes~~
Brute-force check.
Reads line of space-separated digits from stdin. Prints answer to stdout.
```none
perl -aE'@o=0..$#F;for(;;){for$f("d5(d6(d7d))","d5((d6d)7d)","(d5(d6d))7d","(d5d)6(d7d)","((d5d)6d)7d"){map{$_=sprintf$f=~s/d/%d/gr=~s/\d/%$&\$s/gr,@F[@o],/./g;if(24eq eval){say;exit}}glob"{+,-,\\*,/}"x 3}$i=$#o;--$i while$o[$i-1]>$o[$i];$j=$i or last;push@o,reverse splice@o,$i;++$j while$o[$i-1]>$o[$j];@o[$i-1,$j]=@o[$j,$i-1]}say"false"'
```
```bash
perl -aE'
# Fischer-Krause ordered permutation generator (cf. perlfaq4)
# 0. four numbers have been loaded into @F
# initialise list of offsets into @F that will be permuted
~~@o = 0..$#F;~~
# 1. loop over each permutation
for (;;) {
# 2. loop over the 5 possible ways to group operations
# $f is a compacted format string for sprintf
for $f (
"d5(d6(d7d))",
"d5((d6d)7d)",
"(d5(d6d))7d",
"(d5d)6(d7d)",
"((d5d)6d)7d"
){
# 4. loop over each operator combination
map {
# 5. expand the format string
# substitute in the digits and operators
# save resulting expression as $_
$_ =
sprintf
$f =~ s/d/%d/gr
=~ s/\d/%$&\$s/gr,
@F[@o], /./g
;
# 6. execute the expression and test if if equals 24
# if it does, print it and exit
if (24 eq eval) {
say;
exit
}
# 3. generate all combinations of three operators
} glob "{+,-,\\*,/}" x 3
}
# 7. permute the offsets
$i = $#o;
--$i while $o[$i-1]>$o[$i];
$j = $i or last;
push @o, reverse splice @o, $i;
++$j while $o[$i-1]>$o[$j];
@o[$i-1,$j] = @o[$j,$i-1]
}
# 8. if we get here, no solution was found
say "false"
'
```
~~[Try it online!][TIO-mpju627a]~~
[Perl 5]: https://www.perl.org/
[TIO-mpju627a]: https://tio.run/##bZHfjqIwFMbv@xRN7UzKSq1QoJAGw5XJPoOaCQ5FMSgsxVk2hHn0dQskm6yzcMH5fudPv1Nq1ZT@464VzFXa3hsFkU5/IQlAsoUxxNvd@hB/shU7SfB@rq61BHVT3NocohfqrjWMNxDZ@E0CfT/CHPaPpIrXqxVebGVeNURKqzdfnBOU@SQLSCYyy0L2qIzMLCONIlPSZEQ2q8yaS5ENEJn1WIus/prWPX6L9WwD5/GnZhl7ydipGcO9ifHrHmuj7WS7S6qDPdkvcuJ66gdUH2lp9WZJs@MCqq5oQaPM5je4gMYpbJVu4TltbkprAIbhVFZH1C9tau/332w2oA7yARcxXlQSUIoL@PNclApXO1xQ57CZgoPEl9ikzLwy1a2s7/qcVHajPlRj7lrXZfGuDMCFXC7x5T8jLgeZzNo2cTzGF3tKD@MPytNSK/QYwGsuH5z7AtIN5IR3PhUWcLgXjCBgxKGceRbgXEwlgvAlZ2IEYTiCkBFOQ8ZNk@NMTd@vdaV1cSyVQSJ6Rv581j9IfEHujIjoBHUs5gInCMK/lgIWWsD3o2m4bzxHLAKu63mjdonbeUvj2TXP01yzafiMvOD5dBFG0ZdGzqcr6sxL@e@qbovqph80/QM "Perl 5 – Try It Online"

# [Perl 5], 338 bytes
Brute-force check.
Reads line of space-separated digits from stdin. Prints answer to stdout.
```none
perl -aE'@o=0..3;for(;;){for$f("d5(d6(d7d))","d5((d6d)7d)","(d5(d6d))7d","(d5d)6(d7d)","((d5d)6d)7d"){map{$_=sprintf$f=~s/d/%d/gr=~s/\d/%$&\$s/gr,@F[@o],/./g;if(24eq eval){say;exit}}glob"{+,-,\\*,/}"x 3}$i=$#o;--$i while$o[$i-1]>$o[$i];$j=$i or last;push@o,reverse splice@o,$i;++$j while$o[$i-1]>$o[$j];@o[$i-1,$j]=@o[$j,$i-1]}say"false"'
```
```bash
perl -aE'
# Fischer-Krause ordered permutation generator (cf. perlfaq4)
# 0. four numbers have been loaded into @F
# initialise list of offsets into @F that will be permuted
@o = 0..3;
# 1. loop over each permutation
for (;;) {
# 2. loop over the 5 possible ways to group operations
# $f is a compacted format string for sprintf
for $f (
"d5(d6(d7d))",
"d5((d6d)7d)",
"(d5(d6d))7d",
"(d5d)6(d7d)",
"((d5d)6d)7d"
){
# 4. loop over each operator combination
map {
# 5. expand the format string
# substitute in the digits and operators
# save resulting expression as $_
$_ =
sprintf
$f =~ s/d/%d/gr
=~ s/\d/%$&\$s/gr,
@F[@o], /./g
;
# 6. execute the expression and test if if equals 24
# if it does, print it and exit
if (24 eq eval) {
say;
exit
}
# 3. generate all combinations of three operators
} glob "{+,-,\\*,/}" x 3
}
# 7. permute the offsets
$i = $#o;
--$i while $o[$i-1]>$o[$i];
$j = $i or last;
push @o, reverse splice @o, $i;
++$j while $o[$i-1]>$o[$j];
@o[$i-1,$j] = @o[$j,$i-1]
}
# 8. if we get here, no solution was found
say "false"
'
```
[Try it online!][TIO-mpkdcgsy]
[Perl 5]: https://www.perl.org/
[TIO-mpkdcgsy]: https://tio.run/##bZHfjqIwFMbv@xRN7UzKSq1QoJAGw5XJPoOaCQ5FMSgsxVk2hHn0dQskm6yzcMH5fudPv1Nq1ZT@464VzFXa3hsFkU5/IQlAsoUxxNvd@hB/shU7SfB@rq61BHVT3NocohfqrjWMNxDZ@E0CfT/CHPaPpIrXqxWXedUQKa3efHFOUOaTLCCZyCwL2aMyMrOMNIpMSZMR2awyay5FNkBk1mMtsvprWvf4LdazCZzHn5pl7CVjp2YM9ybGr3usjbaT7S6pDvZkvsiJ66kfUH2kpdWbFc2GC6i6ogWNMnvf4AIap7BVuoXntLkprQEYhlNZHVG/tKm933@z2YA6yAdcxHhRSUApLuDPc1EqXO1wQZ3DZgoOEl9ikzLzylS3sr7rc1LZjfpQjblpXZfFuzIAF3K5xJf/jLgcZDJr28TxGF/sKT2MvydPS63QYwCvuXxw7gtIN5AT3vlUWMDhXjCCgBGHcuZZgHMxlQjCl5yJEYThCEJGOA0ZN02OMzV9v9aV1sWxVAaJ6Bn581n/IPEFuTMiohPUsZgLnCAI/1oKWGgB34@m4b7xHLEIuK7njdolbuctjWfXPE9zzabhM/KC59NFGEVfGjmfrqgzL@W/q7otqpt@0PQP "Perl 5 – Try It Online"

#2: Post edited by

jhnc‭ · 2026-05-24T22:47:43Z (4 months ago)
some explanatory comments

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# [Perl 5], 340 bytes
Brute-force check.
Reads line of space-separated digits from stdin. Prints answer to stdout.
```none
perl -aE'@o=0..$#F;for(;;){for$f("d5(d6(d7d))","d5((d6d)7d)","(d5(d6d))7d","(d5d)6(d7d)","((d5d)6d)7d"){map{$_=sprintf$f=~s/d/%d/gr=~s/\d/%$&\$s/gr,@F[@o],/./g;if(24eq eval){say;exit}}glob"{+,-,\\*,/}"x 3}$i=$#o;--$i while$o[$i-1]>$o[$i];$j=$i or last;push@o,reverse splice@o,$i;++$j while$o[$i-1]>$o[$j];@o[$i-1,$j]=@o[$j,$i-1]}say"false"'
```
```bash
perl -aE'
# Fischer-Krause ordered permutation generator (cf. perlfaq4)
@o = 0..$#F;
for (;;) {
for $f (
"d5(d6(d7d))",
"d5((d6d)7d)",
"(d5(d6d))7d",
"(d5d)6(d7d)",
"((d5d)6d)7d"
){
map {
$_ =
sprintf
$f =~ s/d/%d/gr
=~ s/\d/%$&\$s/gr,
@F[@o], /./g
;
if (24 eq eval) {
say;
exit
}
} glob "{+,-,\\*,/}" x 3
}
$i = $#o;
--$i while $o[$i-1]>$o[$i];
$j = $i or last;
push @o, reverse splice @o, $i;
++$j while $o[$i-1]>$o[$j];
@o[$i-1,$j] = @o[$j,$i-1]
}
say "false"
'
```
[Try it online!][TIO-mpju627a]
[Perl 5]: https://www.perl.org/
[TIO-mpju627a]: https://tio.run/##bZHfjqIwFMbv@xRN7UzKSq1QoJAGw5XJPoOaCQ5FMSgsxVk2hHn0dQskm6yzcMH5fudPv1Nq1ZT@464VzFXa3hsFkU5/IQlAsoUxxNvd@hB/shU7SfB@rq61BHVT3NocohfqrjWMNxDZ@E0CfT/CHPaPpIrXqxVebGVeNURKqzdfnBOU@SQLSCYyy0L2qIzMLCONIlPSZEQ2q8yaS5ENEJn1WIus/prWPX6L9WwD5/GnZhl7ydipGcO9ifHrHmuj7WS7S6qDPdkvcuJ66gdUH2lp9WZJs@MCqq5oQaPM5je4gMYpbJVu4TltbkprAIbhVFZH1C9tau/332w2oA7yARcxXlQSUIoL@PNclApXO1xQ57CZgoPEl9ikzLwy1a2s7/qcVHajPlRj7lrXZfGuDMCFXC7x5T8jLgeZzNo2cTzGF3tKD@MPytNSK/QYwGsuH5z7AtIN5IR3PhUWcLgXjCBgxKGceRbgXEwlgvAlZ2IEYTiCkBFOQ8ZNk@NMTd@vdaV1cSyVQSJ6Rv581j9IfEHujIjoBHUs5gInCMK/lgIWWsD3o2m4bzxHLAKu63mjdonbeUvj2TXP01yzafiMvOD5dBFG0ZdGzqcr6sxL@e@qbovqph80/QM "Perl 5 – Try It Online"

# [Perl 5], 340 bytes
Brute-force check.
Reads line of space-separated digits from stdin. Prints answer to stdout.
```none
perl -aE'@o=0..$#F;for(;;){for$f("d5(d6(d7d))","d5((d6d)7d)","(d5(d6d))7d","(d5d)6(d7d)","((d5d)6d)7d"){map{$_=sprintf$f=~s/d/%d/gr=~s/\d/%$&\$s/gr,@F[@o],/./g;if(24eq eval){say;exit}}glob"{+,-,\\*,/}"x 3}$i=$#o;--$i while$o[$i-1]>$o[$i];$j=$i or last;push@o,reverse splice@o,$i;++$j while$o[$i-1]>$o[$j];@o[$i-1,$j]=@o[$j,$i-1]}say"false"'
```
```bash
perl -aE'
# Fischer-Krause ordered permutation generator (cf. perlfaq4)
# 0. four numbers have been loaded into @F
# initialise list of offsets into @F that will be permuted
@o = 0..$#F;
# 1. loop over each permutation
for (;;) {
# 2. loop over the 5 possible ways to group operations
# $f is a compacted format string for sprintf
for $f (
"d5(d6(d7d))",
"d5((d6d)7d)",
"(d5(d6d))7d",
"(d5d)6(d7d)",
"((d5d)6d)7d"
){
# 4. loop over each operator combination
map {
# 5. expand the format string
# substitute in the digits and operators
# save resulting expression as $_
$_ =
sprintf
$f =~ s/d/%d/gr
=~ s/\d/%$&\$s/gr,
@F[@o], /./g
;
# 6. execute the expression and test if if equals 24
# if it does, print it and exit
if (24 eq eval) {
say;
exit
}
# 3. generate all combinations of three operators
} glob "{+,-,\\*,/}" x 3
}
# 7. permute the offsets
$i = $#o;
--$i while $o[$i-1]>$o[$i];
$j = $i or last;
push @o, reverse splice @o, $i;
++$j while $o[$i-1]>$o[$j];
@o[$i-1,$j] = @o[$j,$i-1]
}
# 8. if we get here, no solution was found
say "false"
'
```
[Try it online!][TIO-mpju627a]
[Perl 5]: https://www.perl.org/
[TIO-mpju627a]: https://tio.run/##bZHfjqIwFMbv@xRN7UzKSq1QoJAGw5XJPoOaCQ5FMSgsxVk2hHn0dQskm6yzcMH5fudPv1Nq1ZT@464VzFXa3hsFkU5/IQlAsoUxxNvd@hB/shU7SfB@rq61BHVT3NocohfqrjWMNxDZ@E0CfT/CHPaPpIrXqxVebGVeNURKqzdfnBOU@SQLSCYyy0L2qIzMLCONIlPSZEQ2q8yaS5ENEJn1WIus/prWPX6L9WwD5/GnZhl7ydipGcO9ifHrHmuj7WS7S6qDPdkvcuJ66gdUH2lp9WZJs@MCqq5oQaPM5je4gMYpbJVu4TltbkprAIbhVFZH1C9tau/332w2oA7yARcxXlQSUIoL@PNclApXO1xQ57CZgoPEl9ikzLwy1a2s7/qcVHajPlRj7lrXZfGuDMCFXC7x5T8jLgeZzNo2cTzGF3tKD@MPytNSK/QYwGsuH5z7AtIN5IR3PhUWcLgXjCBgxKGceRbgXEwlgvAlZ2IEYTiCkBFOQ8ZNk@NMTd@vdaV1cSyVQSJ6Rv581j9IfEHujIjoBHUs5gInCMK/lgIWWsD3o2m4bzxHLAKu63mjdonbeUvj2TXP01yzafiMvOD5dBFG0ZdGzqcr6sxL@e@qbovqph80/QM "Perl 5 – Try It Online"

#1: Initial revision by

jhnc‭ · 2026-05-24T14:09:40Z (4 months ago)

Copy Link

Raw

Markdown

# [Perl 5], 340 bytes

Brute-force check.

Reads line of space-separated digits from stdin. Prints answer to stdout.

```none
perl -aE'@o=0..$#F;for(;;){for$f("d5(d6(d7d))","d5((d6d)7d)","(d5(d6d))7d","(d5d)6(d7d)","((d5d)6d)7d"){map{$_=sprintf$f=~s/d/%d/gr=~s/\d/%$&\$s/gr,@F[@o],/./g;if(24eq eval){say;exit}}glob"{+,-,\\*,/}"x 3}$i=$#o;--$i while$o[$i-1]>$o[$i];$j=$i or last;push@o,reverse splice@o,$i;++$j while$o[$i-1]>$o[$j];@o[$i-1,$j]=@o[$j,$i-1]}say"false"'
```


```bash
perl -aE'
    # Fischer-Krause ordered permutation generator (cf. perlfaq4)
    @o = 0..$#F;
    for (;;) {
        for $f (
            "d5(d6(d7d))",
            "d5((d6d)7d)",
            "(d5(d6d))7d",
            "(d5d)6(d7d)",
            "((d5d)6d)7d"
        ){
            map {
                $_ =
                    sprintf
                        $f =~ s/d/%d/gr
                           =~ s/\d/%$&\$s/gr,
                        @F[@o], /./g
                ;
                if (24 eq eval) {
                    say;
                    exit
                }
            } glob "{+,-,\\*,/}" x 3
        }
        $i = $#o;
        --$i while $o[$i-1]>$o[$i];
        $j = $i or last;
        push @o, reverse splice @o, $i;
        ++$j while $o[$i-1]>$o[$j];
        @o[$i-1,$j] = @o[$j,$i-1]
    }
    say "false"
'
```


[Try it online!][TIO-mpju627a]

[Perl 5]: https://www.perl.org/
[TIO-mpju627a]: https://tio.run/##bZHfjqIwFMbv@xRN7UzKSq1QoJAGw5XJPoOaCQ5FMSgsxVk2hHn0dQskm6yzcMH5fudPv1Nq1ZT@464VzFXa3hsFkU5/IQlAsoUxxNvd@hB/shU7SfB@rq61BHVT3NocohfqrjWMNxDZ@E0CfT/CHPaPpIrXqxVebGVeNURKqzdfnBOU@SQLSCYyy0L2qIzMLCONIlPSZEQ2q8yaS5ENEJn1WIus/prWPX6L9WwD5/GnZhl7ydipGcO9ifHrHmuj7WS7S6qDPdkvcuJ66gdUH2lp9WZJs@MCqq5oQaPM5je4gMYpbJVu4TltbkprAIbhVFZH1C9tau/332w2oA7yARcxXlQSUIoL@PNclApXO1xQ57CZgoPEl9ikzLwy1a2s7/qcVHajPlRj7lrXZfGuDMCFXC7x5T8jLgeZzNo2cTzGF3tKD@MPytNSK/QYwGsuH5z7AtIN5IR3PhUWcLgXjCBgxKGceRbgXEwlgvAlZ2IEYTiCkBFOQ8ZNk@NMTd@vdaV1cSyVQSJ6Rv581j9IfEHujIjoBHUs5gInCMK/lgIWWsD3o2m4bzxHLAKu63mjdonbeUvj2TXP01yzafiMvOD5dBFG0ZdGzqcr6sxL@e@qbovqph80/QM "Perl 5 – Try It Online"

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