"Hello World!"Simplistic Hill Climbing Algorithm.This sample is meant to be readable and is not efficient at all, so!!! Do not use in production !!!

hc.kt

import kotlin.math.abs

const val target = "Hello World!"
const val possibilities = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ123456789 .,!?"

val String.fitness: Int get() = // lower fitness better (for this case) fitness of 0 = solution
    indices.sumOf { index ->
        val indexFirst = possibilities.indexOf(target[index])
        val indexSecond = possibilities.indexOf(this[index])
        val high = maxOf(indexFirst, indexSecond)
        val low = minOf(indexFirst, indexSecond)
        if ((high - low) > possibilities.length / 2) {
            abs(high - possibilities.length - low)
        } else {
            high - low
        }
    }

var current = (target.indices).map { possibilities.random() }.joinToString("")

fun main() {
    val startAt = System.currentTimeMillis()

    var iterations = 0
    for (i in target.indices) {
        while (true) {
            iterations++
            val posIndex = possibilities.indexOf(current[i])
            var testPos1 = posIndex + 1
            var testPos2 = posIndex - 1
            if (testPos2 < 0) testPos2 = possibilities.length - 1
            if (testPos1 >= possibilities.length) testPos1 = 0

            val new1 = current.replaceRange(i, i + 1, possibilities[testPos2].toString())
            val new2 = current.replaceRange(i, i + 1, possibilities[testPos1].toString())
            current = when {
                new1.fitness < current.fitness -> new1
                new2.fitness < current.fitness -> new2
                else -> break
            }
        }
    }

    println("Solution \"$current\" found in $iterations iterations and ${System.currentTimeMillis() - startAt}ms")
}