From dac50700b6e1a173654036acc53047090de71aca Mon Sep 17 00:00:00 2001
From: Hubert Van De Walle <hubv@protonmail.com>
Date: Sun, 20 Dec 2020 13:26:08 +0100
Subject: [PATCH] Day20 part2 WIP

---
 days/src/main/kotlin/Day20.kt | 197 ++++++++++++++++++++++++++++++++--
 1 file changed, 186 insertions(+), 11 deletions(-)

diff --git a/days/src/main/kotlin/Day20.kt b/days/src/main/kotlin/Day20.kt
index 694e411..e158fe7 100644
--- a/days/src/main/kotlin/Day20.kt
+++ b/days/src/main/kotlin/Day20.kt
@@ -4,8 +4,10 @@ import be.vandewalleh.aoc.utils.input.Day
 import be.vandewalleh.aoc.utils.input.Groups
 import be.vandewalleh.aoc.utils.input.Input
 import be.vandewalleh.aoc.utils.input.createDay
+import kotlin.math.sqrt
 
 private typealias Tile = Array<CharArray>
+private typealias Grid = Array<Array<Tile>>
 
 @Day(20)
 class Day20(@Groups val input: Input<List<List<String>>>) {
@@ -57,24 +59,197 @@ class Day20(@Groups val input: Input<List<List<String>>>) {
         }
     }
 
-    fun part1() = combine(tiles.map { it.second })
-        .filter { (a, b) -> sideMatches(a, b) }
-        .map { it.toList() }
-        .flatten()
-        .groupBy { it.map { it.toList() } }
-        .values
-        .asSequence()
-        .filter { it.size == 2 }
-        .flatten()
-        .toSet()
+    private fun neighbours(): Map<Int, List<Tile>> {
+        val neighbours = combine(tiles.map { it.second })
+            .filter { (a, b) -> sideMatches(a, b) }
+            .map { it.toList() }
+            .flatten()
+            .groupBy { it.map { it.toList() } }
+            .values
+
+        val map = mutableMapOf<Int, MutableList<Tile>>()
+        for (neighbour in neighbours) {
+            map.computeIfAbsent(neighbour.size) { mutableListOf() }.add(neighbour.first())
+        }
+        return map
+    }
+
+    fun part1() = neighbours()[2]!!
         .map { tile -> tiles.find { it.second === tile }!! }
         .map { it.first.toLong() }
         .reduce { acc, id -> acc * id }
+
+    operator fun Array<Array<Tile?>>.get(x: Int, y: Int): Tile? {
+        if (y < 0 || y > lastIndex) return null
+        val row = get(y)
+
+        return if (x < 0 || x > row.lastIndex) null
+        else row[x]
+    }
+
+    operator fun Array<Array<Tile?>>.set(x: Int, y: Int, tile: Tile) {
+        this[y][x] = tile
+    }
+
+    private fun fillGrid(): Grid {
+        val neighboursSet = neighbours().entries.associate { it.key to it.value.toMutableSet() }
+
+        val size = sqrt(tiles.size.toDouble()).toInt()
+        val grid: Array<Array<Tile?>> = Array(size) { Array(size) { null } }
+
+        for (x in 0 until size) {
+            for (y in 0 until size) {
+                var neighboursCount = 2
+                if (x != 0 && x != size - 1) neighboursCount++
+                if (y != 0 && y != size - 1) neighboursCount++
+
+                val pos = listOf(
+                    x to y - 1,
+                    x + 1 to y,
+                    x to y + 1,
+                    x - 1 to y,
+                )
+
+                val a = pos.mapNotNull { (x, y) -> grid[x, y] }
+
+                val iterator = neighboursSet[neighboursCount]!!.iterator()
+
+                while (iterator.hasNext()) {
+                    val possibility = iterator.next()
+                    val matches = a.count { sideMatches(it, possibility) }
+                    if (matches == a.size) {
+                        grid[x, y] = possibility
+                        iterator.remove()
+                        break
+                    }
+                }
+            }
+        }
+        return grid as Grid
+    }
+
+    private fun correctGrid(grid: Grid): Grid {
+        TODO("flip / rotate every tile")
+    }
+
+    fun part2() {
+        val grid = correctGrid(fillGrid())
+        TODO("remove tile edges")
+    }
 }
 
 fun main() {
     with(createDay<Day20>(
+        """
+            Tile 2311:
+            ..##.#..#.
+            ##..#.....
+            #...##..#.
+            ####.#...#
+            ##.##.###.
+            ##...#.###
+            .#.#.#..##
+            ..#....#..
+            ###...#.#.
+            ..###..###
+
+            Tile 1951:
+            #.##...##.
+            #.####...#
+            .....#..##
+            #...######
+            .##.#....#
+            .###.#####
+            ###.##.##.
+            .###....#.
+            ..#.#..#.#
+            #...##.#..
+
+            Tile 1171:
+            ####...##.
+            #..##.#..#
+            ##.#..#.#.
+            .###.####.
+            ..###.####
+            .##....##.
+            .#...####.
+            #.##.####.
+            ####..#...
+            .....##...
+
+            Tile 1427:
+            ###.##.#..
+            .#..#.##..
+            .#.##.#..#
+            #.#.#.##.#
+            ....#...##
+            ...##..##.
+            ...#.#####
+            .#.####.#.
+            ..#..###.#
+            ..##.#..#.
+
+            Tile 1489:
+            ##.#.#....
+            ..##...#..
+            .##..##...
+            ..#...#...
+            #####...#.
+            #..#.#.#.#
+            ...#.#.#..
+            ##.#...##.
+            ..##.##.##
+            ###.##.#..
+
+            Tile 2473:
+            #....####.
+            #..#.##...
+            #.##..#...
+            ######.#.#
+            .#...#.#.#
+            .#########
+            .###.#..#.
+            ########.#
+            ##...##.#.
+            ..###.#.#.
+
+            Tile 2971:
+            ..#.#....#
+            #...###...
+            #.#.###...
+            ##.##..#..
+            .#####..##
+            .#..####.#
+            #..#.#..#.
+            ..####.###
+            ..#.#.###.
+            ...#.#.#.#
+
+            Tile 2729:
+            ...#.#.#.#
+            ####.#....
+            ..#.#.....
+            ....#..#.#
+            .##..##.#.
+            .#.####...
+            ####.#.#..
+            ##.####...
+            ##..#.##..
+            #.##...##.
+
+            Tile 3079:
+            #.#.#####.
+            .#..######
+            ..#.......
+            ######....
+            ####.#..#.
+            .#...#.##.
+            #.#####.##
+            ..#.###...
+            ..#.......
+            ..#.###...
+        """.trimIndent()
     )) {
-        println(part1())
+        println(part2())
     }
 }