Reverse words

reverseWord.kt

/**
 * Kotlin code challenges. Find related objects
 * playground: https://pl.kotl.in/x4pqB-guK
 */

import java.util.*
import kotlin.collections.ArrayList

fun main() {
    val message = "Hello, world!"

    println("Original: $message \n")
    println("1) ${reverseWords(message)}")
    println("2) ${optimizeReverseWords(message)}")
    println("3) ${reverseWordsByStack(message)}")

}

fun reverseWords(sentence: String): String {
    val words = sentence.split(" ")

    return words.reversed().joinToString(" ")
}

fun reverseWordsByStack(sentence: String): String {
    val words = sentence.split(" ")
    val wordStack: Stack<String> = Stack()
    val reversedWords: ArrayList<String> = arrayListOf()

    for (word in words) {
        wordStack.push(word)
    }

    while(!wordStack.empty()) {
        reversedWords.add(wordStack.pop())
    }

    return reversedWords.joinToString(" ")
}

fun optimizeReverseWords(sentence: String): String {
    val words = sentence.split(" ").toTypedArray()

    val length = words.size
    val center = (length / 2) - 1
    var lastIndex = words.lastIndex

    if (center < 0) {
        return sentence
    }

    for (index in 0..center) {
        words[lastIndex] = words[index].also { words[index] = words[lastIndex] }

        lastIndex -= 1
    }

    return words.joinToString(" ")
}