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https://github.com/eliahkagan/old-practice-snapshot

a bunch of old solutions to coding exercises
https://github.com/eliahkagan/old-practice-snapshot

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a bunch of old solutions to coding exercises

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# old-practice-snapshot - a bunch of old solutions to coding exercises



*My recent solutions are in a different repository,

[**practice**](https://github.com/EliahKagan/practice). You might be looking

for that.*



This is a snapshot, without useful source control history, of my **old

solutions** to coding and algorithms exercises (practice problems / competitive

programming problems). Most are for problems posed on websites and checked with

an online judge, but I’ve also included a small handful of personal

exercises and exercises from books, when they seemed worth including and not

better in any other repository.



I wrote and saved these solutions originally without source control. 😬 (The

directory tree was also almost completely flat.) That was a mistake... but one

that can be partially rectified, because I kept backup files with a systematic

naming scheme--well, a few such schemes--and the [file modification timestamps

are correct](#when-things-are-from), which means it is possible to

automatically generate a repository in which every version of every file has a

commit, the sequence and dates that everything was written are reflected, and

numerous files have useful histories (so `git blame` would often be useful,

etc.). This is to say that it is possible to turn a disadvantage into an

advantage.



**But *this* is not the repository that turns that disadvantage into and

advantage!** No, this is just a snapshot of the whole directory tree in a

single commit. It is far less useful than the proper history-bearing repository

will be once I get around to making it, but perhaps not totally useless. It's

at least useful to me.



This repository does not include recent solutions, which are in the

[**practice**](https://github.com/EliahKagan/practice) repository instead and

not here. That is to say that this repository, old-practice-snapshot, is a

snapshot of old-practice, *not* an old snapshot of practice. Some problems have

solutions in both repositories, but solutions in the practice repository are

not based on solutions here, and often used different techniques or were

otherwise implemented in substantially different ways (though this is not

always the case). There are also many problems here that have no solutions

there, and many problems there that have no solutions here.



## License



This repository is licensed under [0BSD](https://spdx.org/licenses/0BSD.html).

See [**`LICENSE`**](LICENSE).



Some material in this repository is not written by me; for example, problems

sometimes contain scaffolding code written by problem setters, and I've

included some small input test cases. I've only included any material not

written by me when I believe it is clearly fair use. See

[`FAIR-USE.md`](FAIR-USE.md) for details.



## Where things are



Most code in this repository is in the `main` directory. This includes

solutions to numerous HackerRank, Geeksforgeeks, and LeetCode problems, as well

as occasional problems from other websites and sources, and some personal

practice problems.



Several things are better organized and in the `hier` directory, because it

follows a hierarchical organization scheme.



Code that is not for a specific problem but is relevant to multiple problems,

such as Sieve of Eratosthenes implementations written and tested by themselves

and then adapted to various problems, is in `meta`.



## When things are from



Most of the solutions in this repository were written from 2016 to 2018,

heavily tapering off in 2019, though it contains a small amount of code from

2013, 2015, and 2020. This repository does have content from 2021, but it

consists almost entirely of README files and other additions connected to

organizing it and presenting its contents.



```text

$ find . -type f \! -name '.*' -printf '%TY\n' | sort | uniq -c

     16 2013

     20 2015

   1606 2016

   1362 2017

   1592 2018

    356 2019

     45 2020

     38 2021

```



The file timestamps (on regular files, not directories) are correct, but `git`

doesn't retain those automatically. The eventual solution will be to build a

repository, as described above. For this snapshot, I've simply included a 7-zip

archive file, `old-practice-snapshot.7z`, in the root of the repository.

Although there are far more compact alternatives--such as generating a script

that, when run, restores the timestamps--an archive of the files is simple to

include and easy to use, and the increase in size is not severe.