Day 12

day12.kts

@@ -0,0 +1,136 @@
+#!/usr/bin/env kotlin
+import java.util.Scanner
+
+
+val scanner = Scanner(System.`in`)
+
+class Map(private val grid: List<List<String>>) {
+    private val fields = mutableSetOf<Field>()
+    private val map = mutableListOf<List<Plot>>()
+    init {
+        for ((y, line) in grid.withIndex()) {
+            map.add(line.mapIndexed { x, s -> Plot(Pair(x, y), s) })
+        }
+        for (y in 0 until this.getHeight()) {
+            for (x in 0 until this.getWidth()) {
+                val plot = getPlot(x, y)
+                if (!plot.hasField()) {
+                    val field = Field(this)
+                    plot.addField(field)
+                    fields.add(field)
+                    field.expand(plot)
+                }
+            }
+
+        }
+    }
+    fun getWidth(): Int = grid[0].size
+    fun getHeight(): Int = grid.size
+    fun getPlot(x: Int, y: Int): Plot = map[y][x]
+
+    fun getFields(): Set<Field> = fields
+
+    fun getPrice(): Long = fields.sumOf { it.getPrice() }
+    fun getBulkPrice(): Long = fields.sumOf { it.getBulkPrice() }
+
+}
+
+class Field(private val map: Map) {
+    private val fieldPlots = mutableSetOf<Plot>()
+    private val borderPlots = mutableSetOf<Pair<Plot, Plot>>()
+    fun addPlot(plot: Plot) {
+        fieldPlots.add(plot)
+    }
+
+    fun expand(plot: Plot) {
+        val (x, y) = plot.getPosition()
+        val checkPositions = listOf(Pair(x - 1, y), Pair(x + 1, y), Pair(x, y - 1), Pair(x, y + 1))
+        for ((checkX, checkY) in checkPositions) {
+            if (checkX < 0 || checkX >= map.getWidth() || checkY < 0 || checkY >= map.getHeight()) {
+                addBorder(plot, Plot(Pair(checkX, checkY), "."))
+                continue
+            }
+            val checkedPlot = map.getPlot(checkX, checkY)
+            if (plot.getType() == checkedPlot.getType()) {
+                if (!checkedPlot.hasField()) {
+                    checkedPlot.addField(this)
+                    expand(checkedPlot)
+                }
+            } else {
+                addBorder(plot, checkedPlot)
+            }
+        }
+
+    }
+
+    private fun addBorder(plot: Plot, checkedPlot: Plot) {
+        borderPlots.add(Pair(plot, checkedPlot))
+    }
+
+    fun getPrice(): Long {
+        return getArea() * getCircumference()
+    }
+
+    fun getArea(): Long = fieldPlots.size.toLong()
+    fun getCircumference(): Long = borderPlots.size.toLong()
+    fun getBulkPrice(): Long {
+        return getArea() * getNumberOfSides()
+    }
+
+    private fun getNumberOfSides(): Long {
+        val leftBorders = borderPlots.filter { it.first.getPosition().first > it.second.getPosition().first}.map { it.first.getPosition() }
+        val rightBorders = borderPlots.filter { it.first.getPosition().first < it.second.getPosition().first}.map { it.first.getPosition() }
+        val topBorders = borderPlots.filter { it.first.getPosition().second > it.second.getPosition().second}.map { it.first.getPosition() }
+        val bottomBorders = borderPlots.filter { it.first.getPosition().second < it.second.getPosition().second}.map { it.first.getPosition() }
+
+        return countSides(leftBorders) + countSides(rightBorders) + countSides(topBorders) + countSides(bottomBorders)
+    }
+
+    private fun countSides(coordinates: List<Pair<Int, Int>>): Long {
+        val visited = mutableSetOf<Pair<Int, Int>>()
+        val coordinateSet = coordinates.toSet()
+        var sideCount = 0
+        val directions = listOf(Pair(1, 0), Pair(0, 1), Pair(-1, 0), Pair(0, -1))
+
+        fun dfs(coord: Pair<Int, Int>) {
+            val stack = mutableListOf(coord)
+            while (stack.isNotEmpty()) {
+                val current = stack.removeLast()
+                if (current in visited) continue
+                visited.add(current)
+                directions.map { (dx, dy) -> Pair(current.first + dx, current.second + dy) }
+                    .filter { it in coordinateSet && it !in visited }
+                    .forEach { stack.add(it) }
+            }
+        }
+        for (coord in coordinates) {
+            if (coord !in visited) {
+                sideCount++
+                dfs(coord)
+            }
+        }
+
+        return sideCount.toLong()
+    }
+}
+
+class Plot(private val position: Pair<Int, Int>, private val type: String) {
+    private var field: Field? = null
+    fun addField(field: Field) {
+        this.field = field
+        field.addPlot(this)
+    }
+
+    fun hasField(): Boolean = field != null
+    fun getPosition(): Pair<Int, Int> = position
+    fun getType(): String = type
+}
+
+val grid = mutableListOf<List<String>>()
+while (scanner.hasNextLine()) {
+    grid.add(scanner.nextLine().split("").filter { it.isNotEmpty() })
+}
+
+val map = Map(grid.reversed())
+println("The price is: ${map.getPrice()}")
+println("The bulk price is ${map.getBulkPrice()}")

day12.kts.testvalue

@@ -0,0 +1,2 @@
+The price is: 1375476
+The bulk price is 821372