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jamiecurlejamiecurle
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W1/7 - Sparse Array (#152)
There's a bit more to this PR than just the Elixir challenge. The global readme had a big update to link to the PR's for each challenge. That's a nicer pattern than the per week readme which is cumbersome and invisible. This closes #117
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‎README.md‎

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This repo’s layout isn’t idiomatic to any one language — it’s a mix of Elixir, Go, Python, and TypeScript.
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## Quality
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When I first started these challenges, I was in a teaching job and I was completing them between classes and during times when my students had been tasked and was literally doing nothing. These challenges go all the way up to week 4/5. These are not my best work, I was more interested in making stuff work. However, when I quit the teaching job and was able to sit down and focus on quality, I started everything again. I went over the week one python work and moved everything to a standard that any colleage, customer or employer would be more than happy with.
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So below is a table of challenges that I consider to be complete, and to have been completed to a high professional standard that you'd expect from any work I was doing. Inline docs, testing, linting, static code analysis, CI/ CD etc. Each PR for each challenge is listed below. If it's not in this table and it's in the repo, consider it a working draft of my thoughts.
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### Week 1
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| | | Python | Elixir | TypeScript | Go |
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|-|- |- |- |- |- |
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| W1/1| Plus Minus |[![PR](img/pr.svg)][11py]|[![PR](img/pr.svg)][11ex]| ➖ |[![PR](img/pr.svg)][11go]|
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| W1/2| Mini Max Sum |[![PR](img/pr.svg)][12py]|[![PR](img/pr.svg)][12ex]| ➖ |[![PR](img/pr.svg)][11go]|
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| W1/3| Time Conversion |[![PR](img/pr.svg)][13py]|[![PR](img/pr.svg)][13ex]|[![PR](img/pr.svg)][13ts]|[![PR](img/pr.svg)][11go]|
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| W1/4| Breaking Records |[![PR](img/pr.svg)][14py]|[![PR](img/pr.svg)][14ex]| ➖ | ➖ |
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| W1/5| Camel Case |[![PR](img/pr.svg)][15py]|[![PR](img/pr.svg)][15ex]| ➖ | ➖ |
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| W1/6| Divisible Sum Pairs |[![PR](img/pr.svg)][16py]|[![PR](img/pr.svg)][16ex]| ➖ | ➖ |
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| W1/7| Sparse Array |[![PR](img/pr.svg)][17py]|[![PR](img/pr.svg)][17ex]| ➖ | ➖ |
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[11py]: https://github.com/treejamie/hackerrank-90days/pull/108
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[12py]: https://github.com/treejamie/hackerrank-90days/pull/108
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[13py]: https://github.com/treejamie/hackerrank-90days/pull/109
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[14py]: https://github.com/treejamie/hackerrank-90days/pull/111
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[15py]: https://github.com/treejamie/hackerrank-90days/pull/113
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[16py]: https://github.com/treejamie/hackerrank-90days/pull/114
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[17py]: https://github.com/treejamie/hackerrank-90days/pull/115
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[11ex]: https://github.com/treejamie/hackerrank-90days/pull/103
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[12ex]: https://github.com/treejamie/hackerrank-90days/pull/138
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[13ex]: https://github.com/treejamie/hackerrank-90days/pull/141
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[14ex]: https://github.com/treejamie/hackerrank-90days/pull/142
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[15ex]: https://github.com/treejamie/hackerrank-90days/pull/148
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[16ex]: https://github.com/treejamie/hackerrank-90days/pull/151
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[17ex]: https://github.com/treejamie/hackerrank-90days/pull/152
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[11ts]: #
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[12ts]: #
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[13ts]: https://github.com/treejamie/hackerrank-90days/pull/136
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[14ts]: #
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[15ts]: #
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[16ts]: #
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[17ts]: #
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[11go]: https://github.com/treejamie/hackerrank-90days/pull/102
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[12go]: https://github.com/treejamie/hackerrank-90days/pull/105
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[13go]: https://github.com/treejamie/hackerrank-90days/pull/147
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[14go]: #
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[15go]: #
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[16go]: #
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[17go]: #
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### Week 2
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I'll update this README with week two once I've completed all the challenges in all the languages from week one.
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Spot something I could improve? Open an issue and point it out — that would be swell.
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## 🙋 Why?
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What I’m noticing, though, is that it’s also improving my authoring skills more broadly.
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I started in January. At first, I just wanted to get through it in Python — a collection of scripts to store solutions. Then I added per-file unit testing. Then I started doing the challenges in different languages, and it evolved from there. Now it’s basically a code dojo for me, where I’m free to pick a task and write it up in a bunch of languages.
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I started in January. At first, I just wanted to get through it in Python — a collection of scripts to store solutions. Then I added per-file unit testing. Then I started doing the challenges in different languages, and it evolved from there. Now it’s basically a code dojo for me, where I’m working through each challenge in each language. I'm learning a lot. Especially about parsing text files (_test cases_).
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I’ll be very pleased if I complete these challenges by the end of 2025 in four languages: Python, Elixir, Go, and TypeScript. The aim is to get a nice 25% language distribution across the repository and to demonstrate competence in basic project layout, standard libraries, testing methodologies, and — most importantly — low-complexity solutions.
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‎w1/README.md‎

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| Python | Elixir | TypeScript | Go |
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|--------|--------|------------|----|
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| ✅ | ➖ | ➖ | ➖ |
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| ✅ | ✅ | ➖ | ➖ |

‎w1/sparsearray.ex‎

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defmodule HackerRank.W1.SparseArray do
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@moduledoc """
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Sparse Arrays - Challenge 7, Week 1.
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<https://www.hackerrank.com/challenges/three-month-preparation-kit-sparse-arrays/problem>
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"""
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@doc """
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Return a list of counts for how often each query appears in the input strings.
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## Parameters:
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strings (list[str]): a list of strings
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queries (list[str]): a list of queries
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## Returns:
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list[int]: counts for how often each query appears in the input strings.
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## Example:
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iex> SparseArray.challenge(["aba", "baba", "aba", "xzxb"], ["aba", "xzxb", "ab"])
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[2, 1, 0]
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"""
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@spec challenge([String.t()], [String.t()]) :: [integer()]
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def challenge(strings, queries) do
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queries
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|> Enum.map(fn query ->
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# r = Regex.compile!("^#{query}$")
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# Enum.count(strings, fn s -> Regex.match?(r, s) end)
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# Regexs work, but the above regex is effectively checking equality
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# So instead, just compare strings. Same thing, faster result.
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Enum.count(strings, fn s -> s == query end)
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end)
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end
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end

‎w1/sparsearray_test.exs‎

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defmodule HackerRank.W1.SparseArrayTest do
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use ExUnit.Case
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alias HackerRank.Test.Helper
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alias HackerRank.W1.SparseArray
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doctest HackerRank.W1.SparseArray
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@pattern ~w"w1/tc/7_*.txt"
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test "run the tests" do
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Helper.test_all(@pattern, &parse_args/1, &parse_expected/1 )
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|> Enum.each(fn [[strings, queries], expected] ->
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assert SparseArray.challenge(strings, queries) == expected
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end)
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end
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def parse_args(raw) do
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# get the data out of a list
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# get the strings
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[take | list] = raw
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take = String.to_integer(take)
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strings = Enum.take(list, take)
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# get the queries
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[take | list ] = Enum.drop(list, take)
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queries = Enum.take(list, String.to_integer(take))
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# done
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[strings, queries]
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end
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def parse_expected(raw) do
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# Just need to convert the list of strings to integers
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Enum.map(raw, &String.to_integer/1)
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end
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end

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