2020 Day 24 Complete

I made some minor changes to helpers/coordinate... I probably need to go
back and fix several previous years/days.

2020/day24/main.go

@@ -0,0 +1,124 @@
+package main
+
+import (
+	"fmt"
+
+	h "git.bullercodeworks.com/brian/adventofcode/helpers"
+)
+
+const (
+	White = iota
+	Black
+)
+
+var tiles map[h.Coordinate]bool
+
+func init() {
+	tiles = make(map[h.Coordinate]bool)
+}
+
+func main() {
+	fmt.Println("# Day 22")
+	inp := h.StdinToStringSlice()
+
+	solve(inp, h.Atoi(h.OptArgNumber(1, "2")))
+}
+
+func solve(inp []string, part int) {
+	buildTiles(inp)
+	if part == 1 {
+		fmt.Println("## Part 1\nAnswer:", len(tiles))
+	} else {
+		for day := 1; day <= 100; day++ {
+			next := make(map[h.Coordinate]bool)
+			lx, ly, hx, hy := getBordering()
+			for y := ly; y <= hy; y++ {
+				for x := lx; x <= hx; x++ {
+					tst := h.Coordinate{X: x, Y: y}
+					_, ok := tiles[tst]
+					bl := CountTiles(GetAllNeighborCoords(tst))
+					if (ok && !(bl == 0 || bl > 2)) || (!ok && bl == 2) {
+						next[tst] = true
+					}
+				}
+			}
+			tiles = next
+			fmt.Printf("Day %d: %d\n", day, len(next))
+		}
+	}
+}
+
+func getBordering() (int, int, int, int) {
+	lx, ly, hx, hy := h.MAX_INT, h.MAX_INT, h.MIN_INT, h.MIN_INT
+	for k := range tiles {
+		lx = h.Min(lx, k.X)
+		ly = h.Min(ly, k.Y)
+		hx = h.Max(hx, k.X)
+		hy = h.Max(hy, k.Y)
+	}
+	return lx - 1, ly - 1, hx + 1, hy + 1
+}
+
+/*
+   o o
+  o o o
+   o o
+*/
+func buildTiles(inp []string) {
+	for k := range inp {
+		curr := h.Coordinate{}
+		var last rune
+		for _, r := range inp[k] {
+			if r == 'n' || r == 's' {
+				last = r
+				continue
+			}
+			curr = GetNeighborCoord(curr, last+r)
+			last = 0
+		}
+		if v := tiles[curr]; v {
+			delete(tiles, curr)
+		} else {
+			tiles[curr] = true
+		}
+	}
+}
+
+func CountTiles(c []h.Coordinate) int {
+	var ret int
+	for _, v := range c {
+		if _, ok := tiles[v]; ok {
+			ret++
+		}
+	}
+	return ret
+}
+
+func GetAllNeighborCoords(c h.Coordinate) []h.Coordinate {
+	var ret []h.Coordinate
+	for _, v := range []rune{
+		'e', 'n' + 'e', 's' + 'e', 'w', 'n' + 'w', 's' + 'w',
+	} {
+		ret = append(ret, GetNeighborCoord(c, v))
+	}
+	return ret
+}
+
+// Translate hex neighbors into a 2d plane
+func GetNeighborCoord(c h.Coordinate, dir rune) h.Coordinate {
+	switch dir {
+	case 'e':
+		return c.East()
+	case 'n' + 'e':
+		return c.North()
+	case 's' + 'e':
+		return c.South().East()
+	case 'w':
+		return c.West()
+	case 'n' + 'w':
+		return c.North().West()
+	case 's' + 'w':
+		return c.South()
+	}
+	return c
+}