This took me longer than I'd care to admit. I feel like I've built this kind of *neighbor-visiting matrix traverser* many times back in college. The only advice I can really give is to dust off some of those college CS notes, haha.

My code for this is kind of messy, and I thought about cleaning it up and reducing some of the duplication... but I really didn't want to after solving it. But if you have questions, I'm happy to answer!

```
package days
import (
"fmt"
"reflect"
inputs "../inputs"
)
// https://adventofcode.com/2020/day/11
// Eleven : advent of code, day eleven part1 and 2.
func Eleven() {
seatGridAsSlices := inputs.Day11
seatGrid := [][]rune{}
for seatRow := range seatGridAsSlices {
asRunes := []rune(seatGridAsSlices[seatRow])
seatGrid = append(seatGrid, asRunes)
}
snapshot := deepCopy2dSlice(seatGrid)
scannedGrid := seatWalker(seatGrid)
for !reflect.DeepEqual(snapshot, scannedGrid) {
snapshot = deepCopy2dSlice(scannedGrid)
tmp := deepCopy2dSlice(scannedGrid)
scannedGrid = seatWalker(tmp)
}
fmt.Print("(Part1) - Final seat grid with ")
fmt.Print(walkOccupied(scannedGrid))
fmt.Println(" occupied.")
snapshot2 := deepCopy2dSlice(seatGrid)
scannedGrid2 := seatWalker2(seatGrid)
for !reflect.DeepEqual(snapshot2, scannedGrid2) {
snapshot2 = deepCopy2dSlice(scannedGrid2)
tmp := deepCopy2dSlice(scannedGrid2)
scannedGrid2 = seatWalker2(tmp)
}
fmt.Print("(Part2) - Final seat grid with ")
fmt.Print(walkOccupied(scannedGrid2))
fmt.Println(" occupied.")
}
func seatWalker(grid [][]rune) [][]rune {
newGrid := deepCopy2dSlice(grid)
for row, cols := range grid {
for seat := range cols {
if cols[seat] == 'L' && checkOccupied(row, seat, grid) == 0 {
newGrid[row][seat] = '#'
}
if cols[seat] == '#' && checkOccupied(row, seat, grid) >= 4 {
newGrid[row][seat] = 'L'
}
}
}
return newGrid
}
func seatWalker2(grid [][]rune) [][]rune {
newGrid := deepCopy2dSlice(grid)
for row, cols := range grid {
for seat := range cols {
if cols[seat] == 'L' && checkOccupied2(row, seat, grid) == 0 {
newGrid[row][seat] = '#'
}
if cols[seat] == '#' && checkOccupied2(row, seat, grid) >= 5 {
newGrid[row][seat] = 'L'
}
}
}
return newGrid
}
func walkOccupied(grid [][]rune) int {
occupied := 0
for _, cols := range grid {
for seat := range cols {
if cols[seat] == '#' {
occupied++
}
}
}
return occupied
}
func checkOccupied(row int, seat int, grid [][]rune) int {
occupied := 0
/*
col-1,row-1 col,row-1 col+1, row-1
col-1,row X col+1, row
col-1,row+1 col,row+1 col+1,row+1
*/
for x := Max(0, row-1); x <= Min(row+1, len(grid)-1); x++ {
for y := Max(0, seat-1); y <= Min(seat+1, len(grid[0])-1); y++ {
if !(x == row && y == seat) {
if grid[x][y] == '#' {
occupied++
}
}
}
}
return occupied
}
func checkOccupied2(row int, seat int, grid [][]rune) int {
occupied := 0
/*
col-1,row-1 col,row-1 col+1, row-1
col-1,row X col+1, row
col-1,row+1 col,row+1 col+1,row+1
*/
for x := Max(0, row-1); x <= Min(row+1, len(grid)-1); x++ {
for y := Max(0, seat-1); y <= Min(seat+1, len(grid[0])-1); y++ {
if !(x == row && y == seat) {
if grid[x][y] == '#' {
occupied++
} else if grid[x][y] == '.' {
occupied = occupied + checkNextNeighbor(grid, x, y, getDir(row, seat, x, y))
}
}
}
}
return occupied
}
func getDir(row int, seat int, x int, y int) string {
if row == x && seat > y {
return "left"
}
if row == x && seat < y {
return "right"
}
if row > x && seat == y {
return "up"
}
if row < x && seat == y {
return "down"
}
if row > x && seat > y {
return "diagUpLeft"
}
if row < x && seat > y {
return "diagDownLeft"
}
if row > x && seat < y {
return "diagUpRight"
}
if row < x && seat < y {
return "diagDownRight"
}
return ""
}
func checkNextNeighbor(grid [][]rune, x int, y int, dir string) int {
switch dir {
case "left":
if y-1 >= 0 {
if grid[x][y-1] == '.' {
return checkNextNeighbor(grid, x, y-1, "left")
} else if grid[x][y-1] == '#' {
return 1
}
}
case "right":
if y+1 < len(grid[x]) {
if grid[x][y+1] == '.' {
return checkNextNeighbor(grid, x, y+1, "right")
} else if grid[x][y+1] == '#' {
return 1
}
}
case "up":
if x-1 >= 0 {
if grid[x-1][y] == '.' {
return checkNextNeighbor(grid, x-1, y, "up")
} else if grid[x-1][y] == '#' {
return 1
}
}
case "down":
if x+1 < len(grid) {
if grid[x+1][y] == '.' {
return checkNextNeighbor(grid, x+1, y, "down")
} else if grid[x+1][y] == '#' {
return 1
}
}
case "diagUpLeft":
if x-1 >= 0 && y-1 >= 0 {
if grid[x-1][y-1] == '.' {
return checkNextNeighbor(grid, x-1, y-1, "diagUpLeft")
} else if grid[x-1][y-1] == '#' {
return 1
}
}
case "diagDownLeft":
if x+1 < len(grid) && y-1 >= 0 {
if grid[x+1][y-1] == '.' {
return checkNextNeighbor(grid, x+1, y-1, "diagDownLeft")
} else if grid[x+1][y-1] == '#' {
return 1
}
}
case "diagUpRight":
if x-1 >= 0 && y+1 < len(grid[x]) {
if grid[x-1][y+1] == '.' {
return checkNextNeighbor(grid, x-1, y+1, "diagUpRight")
} else if grid[x-1][y+1] == '#' {
return 1
}
}
case "diagDownRight":
if x+1 < len(grid) && y+1 < len(grid[x]) {
if grid[x+1][y+1] == '.' {
return checkNextNeighbor(grid, x+1, y+1, "diagDownRight")
} else if grid[x+1][y+1] == '#' {
return 1
}
}
default:
return 0
}
return 0
}
// Max returns the larger of x or y.
func Max(x, y int) int {
if x < y {
return y
}
return x
}
// Min returns the smaller of x or y.
func Min(x, y int) int {
if x > y {
return y
}
return x
}
func prettyGrid(seatGrid [][]rune) {
for runes := range seatGrid {
for rune := range seatGrid[runes] {
fmt.Print(string(seatGrid[runes][rune]))
}
fmt.Println()
}
}
func deepCopy2dSlice(twoDimensionalSlice [][]rune) [][]rune {
copySlice := make([][]rune, len(twoDimensionalSlice))
for i := range twoDimensionalSlice {
copySlice[i] = make([]rune, len(twoDimensionalSlice[i]))
copy(copySlice[i], twoDimensionalSlice[i])
}
return copySlice
}
```

## Discussion (6)

Hey that looks curios I gotta look at it later on my pc ;) I made this one in go as wellðŸ˜…

Nice!

Yeah I don't think my solution is the most

elegantbut also pretty wordy because of Go's lack of generics. I am enjoying it though!yeah thats the beauty you always know what your code will doðŸ˜… wanna see my version?

Link it!

dev.to/gubesch/comment/194en

posted it here yesterday ;)

how did you do today ;)

Been a little busy, but got part1 done! I know what I want to do for part 2. Just gotta get to it ðŸ˜¬