The python solutions are my attempts to place on the leaderboard. Usually I butcher day 1 when solving day 2. Sometimes I restore / tidy the code before pushing to GitHub. Most of the time I won't. There's many better written python solutions on the internet. With these, I finished twelfth on the global leaderboard!
View these on my website: http://arnavsastry.com/c_art/.
The C solutions are compiled with gcc on OSX:
$ gcc --version
Configured with: --prefix=/Library/Developer/CommandLineTools/usr --with-gxx-include-dir=/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/usr/include/c++/4.2.1
Apple clang version 12.0.0 (clang-1200.0.26.2)
Target: x86_64-apple-darwin19.6.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin
and compiled with -Wall (but not -Werror). In an effort to avoid the
5-character stdin token or format strings, I sometimes call gets, which is
deprecated in C99, removed in later editions of the C standard, and horribly
unsafe. Interestingly on OSX, using gets prints a runtime warning, but no
compile time warnings.
To compile a solution:
gcc -Wall -Werror -o day02.out day02.c
For the part 1 answer:
./day02.out < day02.in
For the part 2 answer:
./day02.out part2 < day02.in
In general, you can switch between part 1 and part 2 by passing any command line argument.
I don't have many strict rules for myself, but I'm trying to hold myself to this standard:
- Minimize spaces beyond the "hole" or between a type and identifier
- No manually editing the input file (this is unlikely to budge)
- No defines
- No implicit int declarations
- No external libraries (will definitely break if hashtables or hashing is strictly needed, but probably won't stray from this list)
I might break some of these "rules" as the days get harder.
This isn't code golf: the goal is to use as many short tokens as possible, even if you use a few bytes. Longer tokens are exponentially harder to work with than short tokens. Here are some tricks I've found that can save some tokens:
String concatenation in C just works if you surround both parts with quotes, with no operator in between. This adds several characters though, so try and avoid it.
const char* s = "hello "
"world";For loops are much more manageable than while loops
for(;<cond>;){
// stuff
}You can break up longer integer constants using math, but this will add more characters
assert(2020 == (99+2)*20)Ternary statements are shorter than if statements, even if you don't have an else block.
if (x) {
y = z;
}is equivalent to
x?y=z:0;Use integer literals instead of character literals. It makes the code less readable, but was this ever readable?
There are also many different tricks to pad with extra characters as needed. For example:
/* ADD 1 CHAR */
/* empty statements */
int x = 0;;
/* unary plus */
int x = +0;
/* ADD 2 CHAR */
/* extra scope blocks */
for (/**/) {{ }}
/* trailing comment slashes */
int x = 0;//
/* bonus parens */
int y = (5);
/* ref and deref */
int x = *&y;
/* identity for bools */
int x = !!x;
/* ADD 4+ CHAR */
/**/It's best to re-arrange the code so the long tokens are at the beginning and
ends. Unavoidable long tokens are usually format strings, input parsing
functions like scanf and gets, and printf.