import kotlin.random.Random

fun main() {
    for (size in 1..100){
        val train = Train(size)
        //Switch of the light at position, where we woke up
        train.setSwitchState(false)
        val calculatedSize=calculateTrainSize(train)
        println("$calculatedSize==$size")
    }
}

fun calculateTrainSize(train: Train, steps: Int = 1): Int {
    //Move left by the indicated value of steps and switch off the light
    repeat(steps) {train.moveLeft()}
    train.setSwitchState(false)
    //Move backward to the initial position and move right by the indicated values of steps and switch off the light
    repeat(steps*2) {train.moveRight()}
    train.setSwitchState(false)
    //Move left to the position where we previously switched off the light and switch on it is
    repeat(steps*2) {train.moveLeft()}
    train.setSwitchState(true)
    //Move right to the position where we previously switched off the light and checking if it was switched on
    repeat(steps * 2) {
        train.moveRight()
        //We can be sure that we switched off it earlier and if it is turned on then we walk in a circle
        if (train.getSwitchState())
            return it+1;
    }
    //Move back to switched on light and switch off it for next iteration
    repeat(steps * 2) { train.moveLeft() }
    train.setSwitchState(false)
    //Move to the position where we woke up
    repeat(steps) { train.moveRight() }
    //Try to move on one more step
    return calculateTrainSize(train, steps + 1)
}

class Train(private val size: Int) {
    init {
        if (size<1)
            throw IllegalArgumentException("Argument size must be >=1, otherwise the task doesn't make sense")
    }

    //Array of train switches with random initial state
    private val trainSwitches = BooleanArray(size).map { Random.nextBoolean() }.toMutableList()
    // Current position in the train, initial value generated randomly
    var position: Int = (0 until size).random()

    fun setSwitchState(isOn: Boolean) {
        trainSwitches[position] = isOn
    }

    fun getSwitchState(): Boolean {
        return trainSwitches[position]
    }

    fun moveLeft(): Int {
        if (--position < 0)
            position = size-1
        return position
    }

    fun moveRight(): Int {
        if (++position >= size)
            position = 0
        return position
    }
}