KotlinPlayground

gistfile1.txt

fun main() {
    val list = listOf<Int>(1, 2, 3, 2, 1)
    println(
        "the pivot index is: ${
            searchIndex(
                list,
                0,
                list.size - 1,
                null,
                { mid -> mid == 0 || mid == list.size - 1 },
                { mid -> list[mid] > list[mid - 1] && list[mid] > list[mid + 1] },
                { mid -> list[mid] > list[mid - 1] && list[mid] < list[mid + 1] })
        } "
    )


    val sortedList = listOf<Int>(1, 2, 3, 4,5,7,8,9)
    val target  =8
    println(
        "the index of $target is: ${
            searchIndex(
                sortedList,
                0,
                sortedList.size - 1,
                target,
                { _ ->false },
                { mid -> sortedList[mid]== target },
                { mid -> target> sortedList[mid] })
        } "
    )

}

fun searchIndex(
    list: List<Int>,
    startingIndex: Int,
    endingIndex: Int,
    target: Int? = null,
    firstCondition: (mid: Int) -> Boolean,
    secondCondition: (mid: Int) -> Boolean,
    thirdCondition: (mid: Int) -> Boolean,
): Int {
    val mid = (startingIndex + endingIndex) / 2
    if (startingIndex > endingIndex) {
        return -1
    }

    return when {
        firstCondition(mid) -> -1
        secondCondition(mid) -> mid
        thirdCondition(mid) -> searchIndex(
            list,
            mid + 1,
            endingIndex,
            target,
            firstCondition,
            secondCondition,
            thirdCondition

        )
        else -> searchIndex(
            list, startingIndex,
            mid - 1,
            target,
            firstCondition,
            secondCondition,
            thirdCondition
        )
    }

}