From ed95f875ad46c219b39e583bae279e25ca58aa9a Mon Sep 17 00:00:00 2001
From: Anna Wiggins <annabunches@gmail.com>
Date: Fri, 25 Dec 2020 21:18:34 +0000
Subject: [PATCH] Day 24 solved.

---
 2020/day24.go | 98 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 98 insertions(+)
 create mode 100644 2020/day24.go

diff --git a/2020/day24.go b/2020/day24.go
new file mode 100644
index 0000000..d996917
--- /dev/null
+++ b/2020/day24.go
@@ -0,0 +1,98 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"git.annabunch.es/annabunches/adventofcode/2020/lib/util"
+)
+
+func parseInput(input []string) map[[2]int]bool {
+	tiles := make(map[[2]int]bool)
+	for _, line := range input {
+		coords := [2]int{0, 0}
+		for i := 0; i < len(line); i++ {
+			switch line[i] {
+			case 'e':
+				coords[0]++
+			case 'w':
+				coords[0]--
+			case 'n':
+				next := line[i+1]
+				switch next {
+				case 'e':
+					coords[0]++
+					coords[1]--
+				case 'w':
+					coords[1]--
+				}
+				i++
+			case 's':
+				next := line[i+1]
+				switch next {
+				case 'e':
+					coords[1]++
+				case 'w':
+					coords[0]--
+					coords[1]++
+				}
+				i++
+			}
+		}
+		if tile, ok := tiles[coords]; ok && tile == true {
+			tiles[coords] = false
+		} else {
+			tiles[coords] = true
+		}
+	}
+
+	return tiles
+}
+
+func runGeneration(oldGen map[[2]int]bool) map[[2]int]bool {
+	counts := make(map[[2]int]int)
+	newGen := make(map[[2]int]bool)
+
+	for coords, live := range oldGen {
+		if live {
+			counts[[2]int{coords[0] + 1, coords[1]}]++
+			counts[[2]int{coords[0] - 1, coords[1]}]++
+			counts[[2]int{coords[0], coords[1] + 1}]++
+			counts[[2]int{coords[0], coords[1] - 1}]++
+			counts[[2]int{coords[0] + 1, coords[1] - 1}]++
+			counts[[2]int{coords[0] - 1, coords[1] + 1}]++
+		}
+	}
+
+	for coords, count := range counts {
+		if oldGen[coords] && count <= 2 {
+			newGen[coords] = true
+		}
+		if !oldGen[coords] && count == 2 {
+			newGen[coords] = true
+		}
+	}
+
+	return newGen
+}
+
+func main() {
+	step := os.Args[1]
+	values := util.InputParserStrings(os.Args[2])
+
+	tiles := parseInput(values)
+
+	if step == "2" {
+		for i := 0; i < 100; i++ {
+			tiles = runGeneration(tiles)
+		}
+	}
+
+	count := 0
+	for _, v := range tiles {
+		if v == true {
+			count++
+		}
+	}
+	fmt.Println(count)
+}