gistfile1.js

    fun validMountainArray(arr: IntArray): Boolean {
        if (arr.size < 3 || arr[0] > arr[1]) return false
        var ascend = true
        for (i in 1 until arr.size) {
            if (arr[i - 1] == arr[i]) return false
            if (ascend) {
                if (arr[i - 1] > arr[i]) ascend = false
            } else {
                if (arr[i - 1] < arr[i]) return false
            }
        }

        return !ascend
    }