C++

This post was originally written on Codeforces; relevant discussion can be found here. TL;DR Use the following template (C++20) for efficient and near-optimal binary search (in terms of number of queries) on floating point numbers. Template template <std::size_t N_BITS> using int_least_t = std::conditional_t< N_BITS <= 8, std::uint8_t, std::conditional_t< N_BITS <= 16, std::uint16_t, std::conditional_t< N_BITS <= 32, std::uint32_t, std::conditional_t< N_BITS <= 64, std::uint64_t, std::conditional_t<N_BITS <= 128, __uint128_t, void>>>>>; // this should work for float and doubles, but for long doubles, std::bit_cast will fail on most systems due to being 80 bits wide....

This post was originally written on Codeforces; relevant discussion can be found here. Someone asked me about my template that used a “cache wrapper” for lambdas, so I decided to write a post explaining how it works. For reference, here is a submission of mine from 2021 that uses that template. Here’s what you will find implementations for in this post: Generalized hashing (for tuple types, sequence types and basic types) Convenient aliases for policy based data structures Wrappers for recursive (or otherwise) lambdas that automatically do caching (memoization) for you....

This post was originally written on Codeforces; relevant discussion can be found here. Disclaimer: This post (and all of my other posts, unless specified otherwise) is 100% ChatGPT-free — there has been no use of any AI/ML-based application while coming up with the content of this post. The reason and an appeal There is a lot of AI-generated content out there these days that sounds plausible and useful but is absolute garbage and contributes nothing beyond a list of superficial sentences — even if it has content that is true (which is a big IF, by the way), it generates content that you could have just looked up on your favorite search engine....

This post was originally written on Codeforces; some relevant discussion can be found here. Note: for those who don’t like using the post-increment operator (i++), hopefully this post convinces you that it is not just a convention that C programmers coaxed the world into following out of tradition. Also, all of the following discusses the increment operators in C++, and not C, where the semantics are slightly different. Disclaimer: I use ++i much more often in code....

This post was originally written as a feature request for Codeforces; some relevant discussion can be found here. I believe that adding the Boost library on Codeforces would be a great addition for C++ competitive programmers. AtCoder already supports it (alongside GMP and Eigen, but Boost has replacements/wrappers for those: Boost.Multiprecision and Boost.uBLAS). CodeChef supports it too (or at least used to support it at some point, not sure now). I’ve seen at least 3 posts by people trying to use Boost on Codeforces and failing, and on thinking about it, I couldn’t really come up with a good reason (in my opinion) that Boost should not be supported on Codeforces....

This post was originally written on Codeforces; relevant discussion can be found here. People often say C++ is much more cumbersome to write than any sane language should be, but I think that is mainly due to lack of knowledge about how to write modern C++ code. Here’s how you can write code more smartly and succinctly in C++(20): Negative indexing with end Have you ever found yourself using a vector like a stack just because you have to also access the last few positions, or writing a sliding window code using a deque (where the size might be variable, but you want to access an element at some offset from the end)?...