RandomQuestion.kt

import java.util.*

/**
 * Created by hwanik on 2017. 6. 9..
 */
fun main(args: Array<String>) {
    val max = 5

    try {
        println("랜덤숫자: ${getRandom(max)}")
    } catch (e: IllegalArgumentException) {
        println("제한된 범위의 숫자입니다. max값은 양수여야 합니다.")
    }
}

fun getZeroOrOne(): Int {
    return Random().nextInt(2)
}

fun getRandom(max: Int): Int {
    if (max < 0) {
        throw IllegalArgumentException()
    } else if (max <= 1) {
        return 0
    }

    val IN_FRONT = 0
    val BINARY_NUMBER = 2
    val maxToBinary = Integer.toBinaryString(max)
    val randomNumber = StringBuilder()

    var i = 0
    var randomNumberToInt = 0

    while (i < maxToBinary.length) {
        randomNumber.insert(IN_FRONT, getZeroOrOne())
        i++

        randomNumberToInt = Integer.parseInt(randomNumber.toString(), BINARY_NUMBER)

        if (randomNumberToInt >= max) {
            randomNumber.setLength(0)
            i = 0
        }
    }

    return randomNumberToInt
}