d11

d11/common.go

@@ -0,0 +1,56 @@
+package d11
+
+import (
+	"strconv"
+	"strings"
+)
+
+type octopus struct {
+	energy  int
+	flashed bool
+}
+
+type grid [][]octopus
+
+func createGrid(in string) grid {
+	lines := strings.Split(strings.TrimSpace(in), "\n")
+	grid := make(grid, len(lines))
+
+	for i, line := range lines {
+		energies := strings.Split(line, "")
+		grid[i] = make([]octopus, len(energies))
+		for j, energy := range energies {
+			num, _ := strconv.Atoi(energy)
+			grid[i][j] = octopus{num, false}
+		}
+	}
+
+	return grid
+}
+
+func incr(x, y int, grid grid) int {
+	if x < 0 || x >= len(grid[0]) || y < 0 || y >= len(grid) {
+		return 0
+	}
+
+	if grid[y][x].flashed {
+		return 0
+	}
+
+	grid[y][x].energy++
+
+	if grid[y][x].energy == 10 {
+		grid[y][x].energy = 0
+		grid[y][x].flashed = true
+		return incr(x-1, y-1, grid) +
+			incr(x, y-1, grid) +
+			incr(x+1, y-1, grid) +
+			incr(x-1, y, grid) +
+			incr(x+1, y, grid) +
+			incr(x-1, y+1, grid) +
+			incr(x, y+1, grid) +
+			incr(x+1, y+1, grid) + 1
+	}
+
+	return 0
+}

d11/d11_test.go

@@ -0,0 +1,37 @@
+package d11
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestP1(t *testing.T) {
+	input := `5483143223
+2745854711
+5264556173
+6141336146
+6357385478
+4167524645
+2176841721
+6882881134
+4846848554
+5283751526`
+
+	assert.EqualValues(t, 1656, P1(input))
+}
+
+func TestP2(t *testing.T) {
+	input := `5483143223
+2745854711
+5264556173
+6141336146
+6357385478
+4167524645
+2176841721
+6882881134
+4846848554
+5283751526`
+
+	assert.EqualValues(t, 195, P2(input))
+}

d11/p1.go

@@ -0,0 +1,28 @@
+package d11
+
+func reset(grid grid) {
+	for y, line := range grid {
+		for x := range line {
+			grid[y][x].flashed = false
+		}
+	}
+}
+
+func flash(grid grid) int {
+	lights := 0
+	for i := 0; i < 100; i++ {
+		for y, line := range grid {
+			for x := range line {
+				lights += incr(x, y, grid)
+			}
+		}
+		reset(grid)
+	}
+
+	return lights
+}
+
+func P1(in string) int {
+	grid := createGrid(in)
+	return flash(grid)
+}

d11/p2.go

@@ -0,0 +1,35 @@
+package d11
+
+func isAllFlashed(grid grid) bool {
+
+	for y, line := range grid {
+		for x := range line {
+			if !grid[y][x].flashed {
+				return false
+			}
+		}
+	}
+
+	return true
+}
+
+func flash2(grid grid) int {
+	step := 0
+	for {
+		for y, line := range grid {
+			for x := range line {
+				incr(x, y, grid)
+			}
+		}
+		step++
+		if isAllFlashed(grid) {
+			return step
+		}
+		reset(grid)
+	}
+}
+
+func P2(in string) int {
+	grid := createGrid(in)
+	return flash2(grid)
+}

main.go

@@ -9,6 +9,7 @@ import (
 	"github.com/fotonmoton/aoc2021/client"
 	"github.com/fotonmoton/aoc2021/d1"
 	"github.com/fotonmoton/aoc2021/d10"
+	"github.com/fotonmoton/aoc2021/d11"
 	"github.com/fotonmoton/aoc2021/d2"
 	"github.com/fotonmoton/aoc2021/d3"
 	"github.com/fotonmoton/aoc2021/d4"
@@ -49,4 +50,6 @@ func main() {
 	fmt.Printf("day 9 part 2: %v\n", d9.P2(client.Day(9)))
 	fmt.Printf("day 10: %v\n", d10.P1(client.Day(10)))
 	fmt.Printf("day 10 part 2: %v\n", d10.P2(client.Day(10)))
+	fmt.Printf("day 11: %v\n", d11.P1(client.Day(11)))
+	fmt.Printf("day 11 part 2: %v\n", d11.P2(client.Day(11)))
 }