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Toy Robot notes

Robot on infinite plane.

import kotlin.math.absoluteValue
fun main() {
    val instructions = "R3L2R7L4"
    val distance = robotDistance(instructions)
    println("hello world $distance")
}
enum class Direction {
    NORTH {
        override fun right() = EAST
        override fun left() = WEST
    },
    SOUTH {
        override fun right() = WEST
        override fun left() = EAST
    },
    EAST {
        override fun right() = SOUTH
        override fun left() = NORTH
    },
    WEST {
        override fun right() = NORTH
        override fun left() = SOUTH
    };
    abstract fun right(): Direction
    abstract fun left(): Direction
}
data class RobotState(val x: Int = 0, val y: Int = 0, val direction: Direction = Direction.NORTH) {
    fun right(): RobotState = this.copy(direction = direction.right())
    fun left(): RobotState = this.copy(direction = direction.left())
    fun move(distance: Int) = when(direction) {
        Direction.NORTH -> copy(y = y + distance)
        Direction.EAST -> copy(x = x + distance)
        Direction.SOUTH -> copy(y = y - distance)
        Direction.WEST -> copy(x = x - distance)
    }
}
fun robotDistance(instructions: String): Int {
    val regex = Regex("(R|L|\\d+)")
    val tokens = regex.findAll(instructions).map { it.groupValues[1] }
    val finalState = tokens.fold(RobotState()) { acc: RobotState, token: String ->
        when (token) {
            "R" -> acc.right()
            "L" -> acc.left()
            else -> acc.move(token.toInt())
        }
    }
    return finalState.x.absoluteValue + finalState.y.absoluteValue
}

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