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 24") 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 }