TCO.kt

import kotlin.time.ExperimentalTime
import kotlin.time.measureTimedValue

@OptIn(ExperimentalTime::class)
fun main() {
    val time = measureTimedValue {
        (1L..50L).map(::fibRec).let(::println)
    }
    println(time)
}

fun fib(num: Long): Long {
    return when (num) {
        0L -> 0L
        1L -> 1L
        else -> fib(num - 1) + fib(num - 2)
    }
}

tailrec fun fibRec(num: Long, aux: Long = 1, acc: Long = 0): Long {
    return when (num) {
        0L -> acc
        1L -> aux
        else -> fibRec(num - 1, acc + aux, aux)
    }
}

fun fibonacciFold(n: Int) =
    (2 until n).fold(1 to 1) { (prev, curr), _ ->
        curr to (prev + curr)
    }.second

fun fat(num: Long): Long {
    return when (num) {
        1L -> num
        else -> num * fat(num - 1)
    }
}

tailrec fun fatRec(num: Long, acc: Long = 1): Long {
    return when (num) {
        1L -> acc
        else -> fatRec(num - 1, acc * num)
    }
}