parenthesis.kt

import java.util.*

fun doit(array: CharArray, left: Int, balance: Int) {
    if (left == 0) {
        println(Arrays.toString(array))
        return
    }
    if (left > balance) {
        array[array.size - left] = '('
        doit(array, left - 1, balance + 1)
    }
    if (balance > 0) {
        array[array.size - left] = ')'
        doit(array,  left - 1, balance - 1)
    }
}

val len = 3 * 2
val array = CharArray(len) { '-' }
doit(array, len, 0)