2023 - Day12 - part 1 - dynamic programming - phuuuu

fmmr · Dec 12, 2023 · c1532eb · c1532eb
1 parent 996b246
commit c1532eb
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diff --git a/src/main/kotlin/no/rodland/advent_2023/Day12.kt b/src/main/kotlin/no/rodland/advent_2023/Day12.kt
@@ -5,25 +5,82 @@ import no.rodland.advent.Day
 // template generated: 12/12/2023
 // Fredrik Rødland 2023
 
-class Day12(val input: List<String>) : Day<Int, Long, List<Pair<String, List<Int>>>> {
+class Day12(val input: List<String>) : Day<Int, Long, List<Day12.Springs>> {
 
     private val parsed = input.parse()
 
     override fun partOne(): Int {
-        return parsed.sumOf { (candidates, numbers) ->
-            expand(candidates)
-                .map { candidate -> candidate.split("\\.+".toRegex()).filterNot { it.isEmpty() } }
-                .filter { it.size == numbers.size }
-                .map { strings -> strings.map { it.length } }
-                .count { it == numbers }
+        return parsed.sumOf { (pattern, numbers) ->
+            count(pattern, numbers).toInt()
         }
     }
 
     override fun partTwo(): Long {
-        return 2
+        return parsed.map { it.expand() }.sumOf { (pattern, numbers) ->
+            count(pattern, numbers)
+        }
+    }
+
+    private val cache = mutableMapOf<Pair<String, List<Int>>, Long>()
+    private fun count(pattern: String, groups: List<Int>): Long {
+        return cache.getOrPut(pattern to groups) {
+            if (pattern.isEmpty()) {
+                return if (groups.isEmpty()) 1L else 0L
+            }
+            when (pattern[0]) {
+                '.' -> count(pattern.drop(1), groups)
+                '#' -> countHash(pattern, groups)
+                '?' -> count(pattern.drop(1), groups) + count(pattern.replaceFirst('?', '#'), groups)
+                else -> error("Should not happen")
+            }
+        }
+    }
+
+    private fun countHash(pattern: String, groups: List<Int>): Long {
+        if (groups.isEmpty()) return 0L
+        val number = groups.first()
+        return when {
+            groups.isEmpty() -> 0L
+            pattern.length < number -> 0L
+            '.' in pattern.substring(0..<number) -> 0L
+            pattern.length == number && groups.size == 1 -> 1L
+            pattern.length == number && groups.size != 1 -> 0L
+            pattern[number] == '#' -> 0L
+            else -> count(pattern.drop(number + 1), groups.drop(1))
+        }
     }
 
 
+    // https://www.reddit.com/r/adventofcode/comments/18ge41g/comment/kd0wo99/
+    // https://github.com/eagely/adventofcode/blob/main/src/main/kotlin/solutions/y2023/Day12.kt
+    private val mem = hashMapOf<Pair<String, List<Int>>, Long>()
+
+    @Suppress("unused")
+    private fun eagely(config: String, groups: List<Int>): Long {
+        if (groups.isEmpty()) return if ("#" in config) 0 else 1
+        if (config.isEmpty()) return 0
+
+        return mem.getOrPut(config to groups) {
+            var result = 0L
+            if (config.first() in ".?")
+                result += eagely(config.drop(1), groups)
+            if (config.first() in "#?" && groups.first() <= config.length && "." !in config.take(groups.first()) && (groups.first() == config.length || config[groups.first()] != '#'))
+                result += eagely(config.drop(groups.first() + 1), groups.drop(1))
+            result
+        }
+    }
+
+    @Suppress("unused")
+    fun bruteForce(): Int {
+        return parsed.sumOf { (patterns, numbers) ->
+            expand(patterns)
+                .map { pattern -> pattern.split("\\.+".toRegex()).filterNot { it.isEmpty() } }
+                .filter { it.size == numbers.size }
+                .map { strings -> strings.map { it.length } }
+                .count { it == numbers }
+        }
+    }
+
     fun expand(input: String): List<String> {
         val count = input.count { it == '?' }
         val numChars = 1 shl count  // 2^count
@@ -33,14 +90,18 @@ class Day12(val input: List<String>) : Day<Int, Long, List<Pair<String, List<Int
             .replace("1", "#")
 
         return (0..<numChars)
-            .map { boolean -> boolean.toMapString() }
+            .map { width -> width.toMapString() }
             .map { mask -> mask.fold(input) { acc: String, c: Char -> acc.replaceFirst("?", c.toString()) } }
     }
 
-    override fun List<String>.parse(): List<Pair<String, List<Int>>> {
+    data class Springs(val pattern: String, val numbers: List<Int>) {
+        fun expand() = Springs(List(5) { pattern }.joinToString("?"), List(5) { numbers }.flatten())
+    }
+
+    override fun List<String>.parse(): List<Springs> {
         return map { line ->
             val (first, second) = line.split(" ")
-            first to second.split(",").map { it.toInt() }
+            Springs(first, second.split(",").map { it.toInt() })
         }
     }
 

diff --git a/src/test/kotlin/no/rodland/advent_2023/Day12Test.kt b/src/test/kotlin/no/rodland/advent_2023/Day12Test.kt
@@ -16,9 +16,9 @@ internal class Day12Test {
     private val test12 = "2023/input_12_test.txt".readFile()
 
     private val resultTestOne = 21
-    private val resultTestTwo = 2L
+    private val resultTestTwo = 525152L
     private val resultOne = 7163
-    private val resultTwo = 2L
+    private val resultTwo = 17788038834112L
 
     val test = defaultTestSuiteParseOnInit(
         Day12(data12),
@@ -29,8 +29,8 @@ internal class Day12Test {
         resultTwo,
         { Day12(data12) },
         { Day12(test12) },
-        numTestPart1 = 1,
-        numTestPart2 = 1,
+        numTestPart1 = 50,
+        numTestPart2 = 50,
     )
 
     @Nested
@@ -108,7 +108,7 @@ internal class Day12Test {
         }
 
         @Test
-        @Slow(10000)
+//        @Slow(10000)
         fun `12,1,live,1`() {
             report(test.livePart1)
         }