dmitrytsyvtsyn/kotlin-algorithms-and-design-patterns

This repository contains the most common algorithms and data structures written in the Kotlin language with simple and concise code.

kotlin-algorithms-and-design-patterns's Issues

observers must be declared as set

private val observers = mutableListOf() // in this line use of mutableSetOf is needed

override fun observe(observer: Observer) {
observers.add(observer)//'cause you can add same observer many times
}

Naive factorial implementation

The current implementation of factorial has two problems:

1. It demonstrates literally nothing except the factorial's definition. To be meaningful it should contain some optimizations like prime factorization.
2. It uses Int, hence it is correct only in [ 0 .. 12 ] range.
   
   Even using ULong will allow values only from 0 to 20 inclusively, so only long arithmetic can have any practical value because for standard integer types the optimal algorithm is just to access array:

val factorials: ULongArray = ulongArrayOf(1uL, 1uL, 2uL ...)

ParenthesisCheck

https://github.com/evitwilly/Kotlin-Algorithms-and-Design-Patterns/blob/develop/src/main/kotlin/other/ParenthesisCheck.kt

В алгоритме не учтен случай, когда в конце строки открывающие скобки, например [[ или ()[

Add visitor pattern

Visitor is one of the few patterns that could be helpfull in Kotlin. I think it would be nice to have it.

sortAlgo -> sortInPlace

https://github.com/KiberneticWorm/Kotlin-Algorithms-and-Design-Patterns/blob/b96f19350f2d70a159eb3310acd31697a73d0ac9/src/main/kotlin/en/sorting/SortAlgo.kt#L10

it would be be better to call it sortInPlace.

Palindrome isNo

Simplest way to make isNo fun is:
fun isNot() = !isYes()

Palindrome algorithm

https://github.com/KiberneticWorm/Kotlin-Algorithms-and-Design-Patterns/blob/master/src/main/kotlin/other/Palindrome.kt
I don't think this is an algorithm.

Factorial loop can be start from 2

fun compute(number: Int) : Int {
var result = 1
for (i in 1..number) { //loop can be i in 2..number as in FactorialBig
result *= i
}
return result
}