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Because it's fun :)↵
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Inspired by [user:SecondThread,2024-10-20]'s comment above, I thought I'd see how hard it would be to solve a Meta Hacker Cup problem at compile time. I chose to start with Round 2 A1, since the input is quite small. This is probably trivial since C++20 and above allow you to allocate memory in constexpr functions, so I gave it a whirl using C++17. This means no allocations are allowed, but the input/output parsing is luckily very straightforward for this problem.↵
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The code is a bit long (118 lines), so I've included it in the link below. It appears to work on the three major compilers: https://godbolt.org/z/cYG1rTfWr (v1) https://godbolt.org/z/3GdPKxrcj (v2).↵
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Note that the compiled binary returns a random value, To actually view the answer, you can view the compiled binary in a hex editor, or do what I did:↵
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~~~~~↵
$ strings a.out | grep Case↵
Case #1: 1↵
Case #2: 4↵
Case #3: 10↵
Case #4: 1↵
Case #5: 1↵
Case #6: 0↵
↵
~~~~~↵
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This code is also sufficient to pass the full data set (136 cases) without running into the default constexpr-ops limit. On my 2,3GHz Intel i5 laptop CPU from 2018, clang compiles the full data set in .5 seconds.↵
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~~Does anyone know a nicer way of ensuring that `ANS` is not discarded by the compiler for not being used?~~ EDIT: Thanks to [user:EnDeRBeaT,2024-11-05] for the `volatile` recommendation, this is much simpler.
↵
Because it's fun :)↵
↵
Inspired by [user:SecondThread,2024-10-20]'s comment above, I thought I'd see how hard it would be to solve a Meta Hacker Cup problem at compile time. I chose to start with Round 2 A1, since the input is quite small. This is probably trivial since C++20 and above allow you to allocate memory in constexpr functions, so I gave it a whirl using C++17. This means no allocations are allowed, but the input/output parsing is luckily very straightforward for this problem.↵
↵
The code is a bit long (118 lines), so I've included it in the link below. It appears to work on the three major compilers: https://godbolt.org/z/cYG1rTfWr (v1) https://godbolt.org/z/3GdPKxrcj (v2).↵
↵
Note that the compiled binary returns a random value, To actually view the answer, you can view the compiled binary in a hex editor, or do what I did:↵
↵
~~~~~↵
$ strings a.out | grep Case↵
Case #1: 1↵
Case #2: 4↵
Case #3: 10↵
Case #4: 1↵
Case #5: 1↵
Case #6: 0↵
↵
~~~~~↵
↵
This code is also sufficient to pass the full data set (136 cases) without running into the default constexpr-ops limit. On my 2,3GHz Intel i5 laptop CPU from 2018, clang compiles the full data set in .5 seconds.↵
↵
~~Does anyone know a nicer way of ensuring that `ANS` is not discarded by the compiler for not being used?~~ EDIT: Thanks to [user:EnDeRBeaT,2024-11-05] for the `volatile` recommendation, this is much simpler.
