robot-journey.kt

/**
 * Problem definition: https://github.com/mikehadlow/Journeys
 * Edit and run this code here: https://pl.kotl.in/_TytttU28
 */
package com.tomkuhn.journey

import com.tomkuhn.journey.Direction.*

enum class Direction { North, East, South, West }

data class Position(val x: Int, val y: Int, val direction: Direction)
data class Problem(val initialPosition: Position, val instructions: String, val expectedFinalPosition: Position)

fun main() {
    val newLine = System.getProperty("line.separator")
    
    fun parseDirection(direction:String) = when(direction){
        "N" -> North
        "E" -> East
        "S" -> South
        else -> West
    }
    
    fun createPositionFromInput(input: List<String>) = Position(input[0].toInt(), input[1].toInt(), parseDirection(input[2]))
    
    fun inputToProblem(inputLines: List<String>) = Problem(createPositionFromInput(inputLines[0].split(" ")),  
                       inputLines[1], 
                       createPositionFromInput(inputLines[2].split(" ")))
    
    val problems = """1 1 E
RFRFRFRF
1 1 E

3 2 N
FRRFLLFFRRFLL
3 3 N

0 3 W
LLFFFLFLFL
2 4 S""".split("$newLine$newLine").map{ inputToProblem(it.split(newLine)) }

	problems.forEach { executeInstructions(it) }
}

fun executeInstructions(problem: Problem) {
    println("Testing problem: $problem")
    
    fun moveForward(position: Position) = when(position.direction){
        North -> position.copy(y = position.y + 1)
        East -> position.copy(x = position.x + 1)
        South -> position.copy(y = position.y - 1)
        West -> position.copy(x = position.x - 1)
    }
    
    fun turnRight(position: Position) = when(position.direction){
        North -> position.copy(direction = East)
        East -> position.copy(direction = South)
        South -> position.copy(direction = West)
        West -> position.copy(direction = North)
    }
    
    fun turnLeft(position: Position) = when(position.direction){
        North -> position.copy(direction = West)
        East -> position.copy(direction = North)
        South -> position.copy(direction = East)
        West -> position.copy(direction = South)
    }
    
    fun executeInstruction(instruction: Char, position: Position) = when(instruction) {
        'L' -> turnLeft(position)
        'R' -> turnRight(position)
        'F' -> moveForward(position)
        else -> position
    }
    
    val finalPosition = problem.instructions.fold(problem.initialPosition) { 
        position: Position, instruction -> executeInstruction(instruction, position)
    }
    
    when(finalPosition == problem.expectedFinalPosition) {
        true -> println("    The final position matches the expected position ${problem.expectedFinalPosition} :)")
        false -> println("    Uh Oh! The final position ${finalPosition} does not match the expected position ${problem.expectedFinalPosition} :(")
    }
}