From 66e48278c5e57d04def8fd08b0b797a504384f5f Mon Sep 17 00:00:00 2001
From: Anna Wiggins <annabunches@gmail.com>
Date: Thu, 17 Dec 2020 05:36:05 +0000
Subject: [PATCH] Day 17 solved

---
 2020/day17.go | 135 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 135 insertions(+)
 create mode 100644 2020/day17.go

diff --git a/2020/day17.go b/2020/day17.go
new file mode 100644
index 0000000..83fef13
--- /dev/null
+++ b/2020/day17.go
@@ -0,0 +1,135 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+
+	"git.annabunch.es/annabunches/adventofcode/2020/lib/util"
+)
+
+func parseInputCubes(input []string) map[[3]int]bool {
+	state := make(map[[3]int]bool)
+	for x, line := range input {
+		for y, char := range line {
+			coords := [3]int{x, y, 0}
+			if char == '#' {
+				state[coords] = true
+			}
+		}
+	}
+
+	return state
+}
+
+func iterateCubes(prev map[[3]int]bool) map[[3]int]bool {
+	counts := make(map[[3]int]int)
+
+	for node, v := range prev {
+		if !v {
+			log.Panicf("Unexpected false value!")
+		}
+		x := node[0]
+		y := node[1]
+		z := node[2]
+		neighbors := make([][3]int, 26)
+		index := 0
+		for i := -1; i < 2; i++ {
+			for j := -1; j < 2; j++ {
+				for k := -1; k < 2; k++ {
+					if i == 0 && j == 0 && k == 0 {
+						continue
+					}
+					neighbors[index] = [3]int{x + i, y + j, z + k}
+					index++
+				}
+			}
+		}
+
+		for _, n := range neighbors {
+			counts[n]++
+		}
+	}
+
+	next := make(map[[3]int]bool)
+	for node, count := range counts {
+		if (prev[node] && count == 2) || count == 3 {
+			next[node] = true
+		}
+	}
+	return next
+}
+
+func parseInputHypercubes(input []string) map[[4]int]bool {
+	state := make(map[[4]int]bool)
+	for x, line := range input {
+		for y, char := range line {
+			coords := [4]int{x, y, 0, 0}
+			if char == '#' {
+				state[coords] = true
+			}
+		}
+	}
+
+	return state
+}
+
+func iterateHypercubes(prev map[[4]int]bool) map[[4]int]bool {
+	counts := make(map[[4]int]int)
+
+	for node, v := range prev {
+		if !v {
+			log.Panicf("Unexpected false value!")
+		}
+		x := node[0]
+		y := node[1]
+		z := node[2]
+		w := node[3]
+		neighbors := make([][4]int, 80)
+		index := 0
+		for i := -1; i < 2; i++ {
+			for j := -1; j < 2; j++ {
+				for k := -1; k < 2; k++ {
+					for l := -1; l < 2; l++ {
+						if i == 0 && j == 0 && k == 0 && l == 0 {
+							continue
+						}
+						neighbors[index] = [4]int{x + i, y + j, z + k, w + l}
+						index++
+					}
+				}
+			}
+		}
+
+		for _, n := range neighbors {
+			counts[n]++
+		}
+	}
+
+	next := make(map[[4]int]bool)
+	for node, count := range counts {
+		if (prev[node] && count == 2) || count == 3 {
+			next[node] = true
+		}
+	}
+	return next
+}
+
+func main() {
+	step := os.Args[1]
+	values := util.InputParserStrings(os.Args[2])
+	switch step {
+	case "1":
+		state := parseInputCubes(values)
+		for i := 0; i < 6; i++ {
+			state = iterateCubes(state)
+		}
+		fmt.Println(len(state))
+	case "2":
+		state := parseInputHypercubes(values)
+		for i := 0; i < 6; i++ {
+			state = iterateHypercubes(state)
+		}
+		fmt.Println(len(state))
+	}
+}