Day 11

src/main/kotlin/com/basdado/adventofcode/Day11.kt

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+package com.basdado.adventofcode
+
+import kotlin.math.roundToInt
+import kotlin.math.sqrt
+import kotlin.system.measureTimeMillis
+
+fun main() {
+    val day = Day11()
+    day.puzzle1()
+    println("Puzzle 2 time: " + (1..10).map { measureTimeMillis { day.puzzle2() } }.average() + " ms")
+}
+
+class Day11 {
+
+    fun puzzle1() {
+
+        val serial = lines("/day/11/input.txt").findFirst().get().toInt()
+        val grid = Array(300) { y -> Array(300) { x -> PowerCell(x, y, serial) } }
+
+        var maxPower = 0
+        var maxPowerX = 0
+        var maxPowerY = 0
+        for (y in 0..297) {
+            for (x in 0..297) {
+                val power = (0..8).map { grid[y + (it / 3)][x + (it % 3)].powerLevel }.sum()
+                if (power > maxPower) {
+                    maxPower = power
+                    maxPowerX = x
+                    maxPowerY = y
+                }
+            }
+        }
+        println("$maxPowerX,$maxPowerY")
+
+    }
+
+    fun puzzle2() {
+        val serial = lines("/day/11/input.txt").findFirst().get().toInt()
+        val grid = Array(300) { y -> Array(300) { x -> PowerCell(x, y, serial) } }
+        val gridSumCache = PowerBlockCache(300, 300, 300)
+        (0 until grid.size).forEach {y -> (0 until grid[0].size).forEach {x ->
+            gridSumCache.set(x, y, 1, grid[y][x].powerLevel)
+        }}
+
+        var maxPower = 0
+        var maxPowerX = 0
+        var maxPowerY = 0
+        var maxSize = 0
+        for (size in 1..grid.size) {
+            for (y in 0 until grid.size) {
+
+                if (size + y > grid.size) {
+                    continue
+                }
+                for (x in 0 until grid[0].size) {
+                    if (size + x > grid[0].size) {
+                        continue
+                    }
+                    val power = powerSum(x, y, size, gridSumCache)
+                    if (power > maxPower) {
+                        maxPower = power
+                        maxPowerX = x
+                        maxPowerY = y
+                        maxSize = size
+                    }
+                }
+            }
+        }
+        println("$maxPowerX,$maxPowerY,$maxSize")
+    }
+
+    private fun powerSum(x: Int, y: Int, size: Int, cache: PowerBlockCache): Int {
+
+        val cached = cache.get(x, y, size)
+        if (cached != null) {
+            return cached
+        } else {
+
+            val powerSum = powerSum(x, y, size - 1, cache) +
+                    powerSum(x + 1, y + 1, size - 1, cache) +
+                    powerSum(x, y + size - 1, 1, cache) +
+                    powerSum(x + size - 1, y, 1, cache) -
+                    if (size > 2) powerSum(x + 1, y + 1, size - 2, cache) else 0
+            cache.set(x, y, size, powerSum)
+            return powerSum
+        }
+    }
+
+    class PowerCell(val x: Int, val y: Int, val gridSerial: Int) {
+        val rackId = x + 10
+
+        val powerLevel = hundreds(((rackId * y) + gridSerial) * rackId) - 5
+    }
+
+    class PowerBlockCache(val maxSize: Int, val maxX: Int, val maxY: Int) {
+        val cache = Array(maxSize) { size -> Array(maxX - size) { Array<Int?>(maxY - size) {null}}}
+
+        fun get(x: Int, y: Int, size: Int): Int? {
+            return cache[size - 1][x][y]
+        }
+
+        fun set(x: Int, y: Int, size: Int, value: Int) {
+            cache[size - 1][x][y] = value
+        }
+    }
+
+    companion object {
+        @JvmStatic
+        fun hundreds(x: Int): Int {
+            return (x - ((x / 1000) * 1000)) / 100
+        }
+
+        @JvmStatic
+        fun divisor(n: Int): Int? {
+            return DEFAULT_DIVISORS.find { n % it == 0 && it < n } ?:
+            (DEFAULT_DIVISORS.last()..sqrt(n.toDouble()).roundToInt()).find { n % it == 0 }
+        }
+
+        private val DEFAULT_DIVISORS = intArrayOf(2, 3, 5, 7, 11, 13, 17, 19)
+    }
+
+    data class PowerBlock(val x: Int, val y: Int, val size: Int)
+}

src/main/resources/day/11/input.txt

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+6303