/*
 * File: subsets.kt
 * Purpose: Prints all subsets of the first n nonnegative integers
 * Compilation: kotlinc subsets.kt
 * Execution: kotlin SubsetsKt n
 *   where n is a positive integer
 * Author: San Skulrattanakulchai
 */

fun main(args: Array<String>) {
    val n = args[0].toInt()
    val b = BooleanArray(n)

    fun subsets(i: Int) {
        if (i == n) {
            for (j in b.indices)
                if (b[j]) print(" $j")
            println()
        } else {
            b[i] = false
            subsets(i+1)
            b[i] = true
            subsets(i+1)
        }
    }

    subsets(0)
}