From cfc8c6a4126bcc7667226a65d6370cd6b39eb4fb Mon Sep 17 00:00:00 2001 From: Cody Boone Ferguson <53008573+xexyl@users.noreply.github.com> Date: Wed, 26 Apr 2023 04:38:26 -0700 Subject: [PATCH] Fix 2004/kopczynski and format fix README.md The fix is that we cannot pass -ON to the compiler. With -ON it enters an infinite loop as the variable l goes up, not down. Format fix README.md. Add kopczynski-a to show what happens when it's not a number. --- 2004/kopczynski/Makefile | 2 +- 2004/kopczynski/README.md | 147 ++++++++++++++++++----------------- 2004/kopczynski/kopczynski-a | 8 ++ 3 files changed, 85 insertions(+), 72 deletions(-) create mode 100644 2004/kopczynski/kopczynski-a diff --git a/2004/kopczynski/Makefile b/2004/kopczynski/Makefile index 51af9451f..4f3266e2f 100644 --- a/2004/kopczynski/Makefile +++ b/2004/kopczynski/Makefile @@ -66,7 +66,7 @@ CINCLUDE= # Optimization # -OPT= -O3 +OPT= # Default flags for ANSI C compilation # diff --git a/2004/kopczynski/README.md b/2004/kopczynski/README.md index d1b6ed156..4b7c8d0d0 100644 --- a/2004/kopczynski/README.md +++ b/2004/kopczynski/README.md @@ -1,12 +1,8 @@ # Best one-liner - Eryk Kopczynski - Faculty of Mathematics, Informatics and Mechanics - ul. Banacha 2 - 02-097 Warszawa - Poland - - http://www.mimuw.edu.pl/~erykk/ +Eryk Kopczynski +Poland + ## To build: @@ -20,6 +16,11 @@ make ./kopczynski < input_file ``` +[Cody Boone Ferguson](/winners.html#Cody_Boone_Ferguson) reported that this +entry cannot be optimised by the compiler if it's to work. He also added the +file [kopczynski-a](kopczynski-a) to demonstrate what happens when art more like +a letter is fed to the program. Thank you Cody! + ## Try: ```sh @@ -31,6 +32,14 @@ make ./kopczynski < kopczynski-11 ``` +Also try: + +```sh +./kopczynski < kopczynski-a +``` + +What happens? + ### Alternate code The judges modified the program to print its result. The original @@ -47,7 +56,7 @@ Then try: echo $? ``` -## Judges' remarks +## Judges' remarks: What is in a line? A lot when you obfuscate the way Eryk Kopczynski did it. This small one line program is an outstanding technical @@ -69,10 +78,10 @@ Here is a related puzzle: how to continue the sequence: 1, 0, 0, 0, 0, 0, 1, 0, 2, 1, ... -With certain arguments, you can alter the exit value. Can you figure +With certain arguments, you can alter the exit value / output. Can you figure out how and why? -## Author's remarks +## Author's remarks: The program proves it is not as hard to recognize numbers. The current one liner version should correctly recognize all numbers from 8 to 11. @@ -81,112 +90,108 @@ recognize negatives, zeros which have dots or slashes inside them, digits should be separated, and numbers should be "complete".) This program returns the number as its exit status. (In most shells, -you can see the exit status of the last command with 'echo $?' (or -just '$?').) +you can see the exit status of the last command with `echo $?` (or +just `$?`).) - [[NOTE: The judges altered the primary version to output a number.]] +**NOTE: The judges altered the primary version to output a number.** On the input, give numbers formed as a sequences of empty spaces and # signs (you can also use dots instead of spaces), ending with an empty line. (No number has an empty line in it.) The program should return the number from 8 to 11 that it thinks it is. -* The line is 131 bytes long (in 1986 165 bytes was OK, and the size +* The line is 131 bytes long (in 1986, 165 bytes was OK, and the size limit has grown from 1986...). * I have decided that it is better for this program to return the number, not to print it, but if you think otherwise, the change would - cost 6 chars (plus a warning). Change 'return *' to 'printf("%d",*)'. - ('$?' is shorter) + cost 6 chars (plus a warning). Change `return *` to `printf("%d",*)`. + (`$?` is shorter) -* I achieved some additional tightness by '-Dif=while', saved 9 chars - of source for cost of 11 chars of build file. If I used '-DB=while', - I would save 12 for 10, but I think the current version is slightly - more obfuscated. +* I achieved some additional tightness by `-Dif=while` which saved 9 chars of +source for the cost of 11 chars of the [Makefile](Makefile). If I used +`-DB=while`, I would save 12 for 10, but I think the current version is slightly +more obfuscated. -* A remark on portability: +### Portability - It only requires two's compliment arithmetics, as far as I - know. The maximum length of an input line is N-9, where - N is the size of int in bits (you can try to compile with - an option '-Dint=long long' for longer lines). +It only requires two's complement arithmetics, as far as I know. The maximum +length of an input line is `N-9`, where `N` is the size of `int` in bits +(you can try to compile with an option `'-Dint=long long'` for longer +lines). - -- Algorithm & Obfuscation -- +### Algorithm & Obfuscation -1. This program works by calculating the Euler characteristics of input, - plus 9. It is the number of digits (i.e. separated #-regions) minus the - number of holes in them. It turns out that this algorithm works - correctly for all numbers from 8 to 11. +1. This program works by calculating the [Euler +characteristics](https://en.wikipedia.org/wiki/Euler_characteristic) of input, +plus 9. It is the number of digits (i.e. separated #-regions) minus the number +of holes in them. It turns out that this algorithm works correctly for all +numbers from 8 to 11. -2. We know that Euler characteristics is the number of "vertexes" +2. We know that [Euler +characteristics](https://en.wikipedia.org/wiki/Euler_characteristic) is the number of "vertexes" - # + # minus the number of "edges" - ## # #. .# - # .# #. ('.' must be empty) + ## # #. .# + # .# #. ('.' must be empty) plus the number of "faces" - ## - ## + ## + ## 3. If we fill all these patterns to 2x2 squares, - #? ## #? #. .# ## - ?? ?? #? .# #. ## - +1 -1 -1 -1 -1 +1 + #? ## #? #. .# ## + ?? ?? #? .# #. ## + +1 -1 -1 -1 -1 +1 - substitute all possible "values" of '?' and sum up, we get that it is + substitute all possible "values" of `?` and sum them up, we get that it is enough to calculate: - #. .# ## - .. #. #. - +1 -1 -1 + #. .# ## + .. #. #. + +1 -1 -1 Note now it is simple and obfuscated enough to be used as a "magic trick". 4. I make a 16-character array; when indexed by 4-bit value which represents the 2x2 squares, it will return a number to add/subtract - {-1,0,+1} + `{-1,0,+1}` -5. We convert lines of input to bitmaps (N-bit integers). Additionally, - it is heavily obfuscated by using negative numbers (two's compliment). - For example, it turns out that 6 in "z=6" in the only 1-digit number - which works here (and it's not only because we have "z>5" in the - following while). The conversion routine also sets n=8 in an obfuscated - and concise way. +5. We convert lines of input to bitmaps (`N-bit` integers). Additionally, it is +heavily obfuscated by using negative numbers (two's complement). For example, +it turns out that `6` in `z=6` is the only 1-digit number which works here (and +it's not only because we have `z>5` in the following `while`). The conversion +routine also sets `n=8` in an obfuscated and concise way. -5. Since we always return the number from 8 to 11, we can calculate - modulo 4. Instead of 16 {-1,0,+1} values, we use a 15-character string - which agrees modulo 4 to the array in (4). (NUL fits very well as the - 16th character, so we use 15-character string.) +6. Since we always return the number from 8 to 11, we can calculate modulo 4. +Instead of `16 {-1,0,+1}` values, we use a 15-character string which agrees +modulo 4 to the array in (`4`). (`NUL` fits very well as the 16th character, so +we use 15-character string.) -6. Since the rule found in (3) did not produce any funny messages, I - changed it until it did. (The # character to find vertexes is in the - top right corner, not the top left one.) The following messages will - also work instead of "has dirtiest IF": +7. Since the rule found in (3) did not produce any funny messages, I changed it until it did. (The `#` character to find vertexes is in the top right corner, not the top left one.) The following messages will also work instead of `has dirtiest IF`: - HighlandYachter - TestDirtiestTen - has lintiest IF - TighterLaughter - HustlerDaughter - TighterDemoThen + HighlandYachter + TestDirtiestTen + has lintiest IF + TighterLaughter + HustlerDaughter + TighterDemoThen They can be mixed, of course! -7. [[NOTE: Item 7 was removed by the judges so as to not spoil the - challenge of figuring how arguments can be used to alter - the exit value.]] +8. NOTE: item 8 was removed by the judges so as to not spoil the challenge of +figuring how arguments can be used to alter the exit value. -8. The variable names are confusing. +9. The variable names are confusing. -9. Finally, the program tries to be as concise as possible. Some - obfuscation comes from this. For additional obfuscation and - conciseness, 'if' means 'while'. +10. Finally, the program tries to be as concise as possible. Some obfuscation +comes from this. For additional obfuscation and conciseness, `if` means `while`. ## Copyright and CC BY-SA 4.0 License: diff --git a/2004/kopczynski/kopczynski-a b/2004/kopczynski/kopczynski-a new file mode 100644 index 000000000..40d5db0ed --- /dev/null +++ b/2004/kopczynski/kopczynski-a @@ -0,0 +1,8 @@ + #### + ###### + ## ## + ### ### + ########## + ## ## + ## ## +