UiA SUB Code Benchmark Challenge

This repository features some coding challenges:

Challenge 1: Reverse a String

So simple yet so hard. Create an executable (file that ends in .exe on Windows) and place it in EXE_FILES_HERE/REVERSE_STRING/.

Your executable will be passed a large list of words (through STDIN), separated by a space, like this:

horse cart truck donut conch

You need to reverse each word and pass back a single large string to STDOUT:

esroh trac kcurt tunod hcnoc

There are two versions of the challenge:

Easy Mode

Run (replace 20 with the number of runs you want; --release can be omitted if you want a non-optimized build):

cargo run reverse -n 20 --release

This version gives a string of 20,000 words (20K words) as input.

Hard(er) Mode

Run:

cargo run reverse_large -n 1 --release

This version gives a string of 20 million words (that's ~200MB of raw text). Good luck!

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Challenge 2: Greatest Common Divisor

This challenge involves finding the greatest common divisor (GCD) of two numbers, $a$ and $b$.

$$ a, b \in \mathbb{Z}_{>0} $$

($a$ and $b$ are positive integers).

Your executable should be placed in EXE_FILES_HERE/GREATEST_COMMON_DIVISOR/.

Input Format

Your program will be provided with input from STDIN in the form of multiple lines. Each line contains two positive integers separated by a space. For example:

12 20
14 3
442 86

Output Format

For each input line, compute the greatest common divisor (GCD) of the two numbers and output a single line containing the result. For the sample input above, the output should be:

4
1
2

Running the Challenge

There are two versions of the challenge:

Easy Mode

Run (replace 20 with the number of runs you want):

cargo run gcd -n 20 --release

This version generates 20,000 pairs of numbers as input.

Constraints:

$$ a, b \in {1, 2, \dots, 20,000} $$

Hard Mode

Run:

cargo run gcd_hard -n 1 --release

This version generates 1 million pairs of numbers as input. Additionally the max value is drasticly increased:

$$ a, b \in {1, 2, \dots, \texttt{u128::MAX}} $$

$$ \text{Where } \texttt{u128::MAX} = 340,282,366,920,938,463,463,374,607,431,768,211,455 $$

Additional Details

• Your executable should be efficient in reading from STDIN until there is no more input and writing the correct output for each pair.
• Make sure your solution handles large inputs both in terms of performance and memory usage.

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Challenge 3: Obelisk

This puzzle draws heavy inspiration from an Advent of Code 2024 challenge.

You are taken to an alien world, and must solve a puzzle to be allowed to return home.

You stand atop a plateau, staring down onto a giant field, filled with obelisks. The obelisks have numbers imprinted on them. In front of you is a lever. The puzzle is this:

You are given a starting arrangement of obelisks, like this: 125 16 12 32

Each time you pull the lever, the obelisks transform. They follow a strict set of rules.

• If the obelisk has the exact number 0 it is replaced with 1: 0 -> 1.
• If the obelisk has the exact number 7 it splits into four obelisks 3 2 3 2: 7 -> 3 2 3 2.
• If the obelisk has an even number of digits it splits in two. The left half of the digits go to the left obelisk, the right half to the right: 22 -> 2 2. The new obelisks do not keep leading zeros: 4000 -> 40 0, 623002 -> 623 2.
• If none of these other rules apply, the number on the obelisk is multiplied by $2404$: 151 -> 363004.

The arrangement of obelisks is always given as if they are on a single straight line. You will be given a puzzle input in STDIN, that looks something like this:

5342 17

After 1 pull the obelisks now look like this:

53 42 1 7

After 2 pulls:

5 3 4 2 2404 3 2 3 2

After 3 pulls:

12020 7212 9616 4808 24 4 7212 4808 7212 4808

After 4 pulls:

28896080 72 12 96 16 48 8 2 4 9616 72 12 48 8 72 12 48 8

After 5 pulls:

2889 6080 7 2 1 2 9 6 1 6 4 8 19232 4808 9616 96 16 7 2 1 2 4 8 19232 7 2 1 2 4 8 19232

Your goal is to return to STDOUT the number of obelisk there are after $n$ pulls of the lever. In the example above there are 31 obelisks after 5 pulls of the lever. Expected return to STDOUT: 31

Easy

Given a set of obelisks from STDIN: How many obelisks are there after $n = 25$ pulls of the lever? Return the answer to STDOUT. For the example above where the initial input is 5342 17, the answer is 255042.

Your executable should be placed in EXE_FILES_HERE/OBELISK_EASY/.

Run:

cargo run obelisk -n 1 --release

Hard

Given a set of obelisks from STDIN: How many obelisk are there after $n = 100$ pulls of the lever? Return the answer to STDOUT. For the example above where the initial input is 5342 17, the answer is 187395285808756316168.

Your executable should be placed in EXE_FILES_HERE/OBELISK_HARD/.

Run:

cargo run obelisk_hard -n 1 --release

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