Created
December 17, 2020 21:01
-
-
Save spellgen/f9b8e940d923040546a80711e451ef1f to your computer and use it in GitHub Desktop.
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| package main | |
| import ( | |
| "bufio" | |
| "fmt" | |
| "os" | |
| "time" | |
| ) | |
| type point struct { | |
| x int | |
| y int | |
| z int | |
| w int | |
| } | |
| const ( | |
| activeRune = '#' | |
| activeByte = byte(activeRune) | |
| inactiveByte = byte('.') | |
| maxIndex = 1000 | |
| ) | |
| var deltaList []point // a list of neighbors around a cube | |
| func init() { | |
| deltaList = make([]point, 0) | |
| for w := -1; w <= 1; w++ { | |
| for z := -1; z <= 1; z++ { | |
| for y := -1; y <= 1; y++ { | |
| for x := -1; x <= 1; x++ { | |
| if !(x == 0 && y == 0 && z == 0 && w == 0) { | |
| deltaList = append(deltaList, point{x, y, z, w}) | |
| } | |
| } | |
| } | |
| } | |
| } | |
| } | |
| func main() { | |
| t1 := time.Now() | |
| var active = make(map[point]bool) | |
| if len(os.Args) < 2 { | |
| panic(fmt.Sprintf("usage: %s <input>", os.Args[0])) | |
| } | |
| fh, err := os.Open(os.Args[1]) | |
| if err != nil { | |
| panic(err) | |
| } | |
| scanner := bufio.NewScanner(fh) | |
| y := 0 | |
| for scanner.Scan() { | |
| for x, r := range scanner.Text() { | |
| if r == activeRune { | |
| active[point{x, y, 0, 0}] = true | |
| } | |
| } | |
| y++ | |
| } | |
| _ = fh.Close() | |
| for k := 0; k < 6; k++ { | |
| active = step(active) | |
| } | |
| fmt.Printf("part 2: %d cubes are active (%s)\n", len(active),time.Now().Sub(t1)) | |
| } | |
| func step(act map[point]bool) map[point]bool { | |
| count := extendedCount(act) | |
| next := make(map[point]bool) | |
| for p, c := range count { | |
| if act[p] { | |
| if c == 2 || c == 3 { | |
| next[p] = true | |
| } | |
| } else { | |
| if c == 3 { | |
| next[p] = true | |
| } | |
| } | |
| } | |
| return next | |
| } | |
| // find the +1 environment around the active cubes | |
| func extendedCount(act map[point]bool) map[point]int { | |
| ext := make(map[point]int) | |
| for p := range act { | |
| for _, d := range deltaList { | |
| ext[point{p.x + d.x, p.y + d.y, p.z + d.z, p.w + d.w}]++ | |
| } | |
| } | |
| return ext | |
| } |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment