2017-day22: game of life from a single virus moving around

2017/day22/main.go

@@ -0,0 +1,115 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"strings"
+
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+func main() {
+	var part int
+	flag.IntVar(&part, "part", 1, "part 1 or 2")
+	flag.Parse()
+	fmt.Println("Running part", part)
+
+	var ans int
+	if part == 1 {
+		ans = part1(util.ReadFile("./input.txt"))
+	} else {
+		ans = part2(util.ReadFile("./input.txt"))
+	}
+	fmt.Println("Output:", ans)
+}
+
+func part1(input string) int {
+	infectedMap := newStateFromInput(input)
+	mid := len(strings.Split(input, "\n")) / 2
+	current := [2]int{mid, mid} // assume square inputs
+
+	// direction starts at 0, i.e. facing up
+	var dirIndex, countBursts int
+
+	for i := 0; i < 10000; i++ {
+		switch infectedMap[current] {
+		case infected:
+			// is infected, turn right
+			dirIndex = (dirIndex + 1) % 4
+			infectedMap[current] = clean
+		case clean:
+			// not infected, turn left
+			dirIndex = (dirIndex + 3) % 4
+			infectedMap[current] = infected
+
+			countBursts++
+		}
+		// move forward
+		current = [2]int{current[0] + dirs[dirIndex][0], current[1] + dirs[dirIndex][1]}
+	}
+
+	return countBursts
+}
+
+func part2(input string) int {
+	state := newStateFromInput(input)
+	mid := len(strings.Split(input, "\n")) / 2
+	current := [2]int{mid, mid}
+
+	var dirIndex, countBursts int
+
+	for i := 0; i < 10000000; i++ {
+		switch state[current] {
+		case clean:
+			dirIndex = (dirIndex + 3) % 4
+			state[current] = weakened
+		case weakened:
+			// keep going in same direction
+			state[current] = infected
+			countBursts++
+		case infected:
+			dirIndex = (dirIndex + 1) % 4
+			state[current] = flagged
+		case flagged:
+			dirIndex = (dirIndex + 2) % 4
+			state[current] = clean
+		default:
+			panic(fmt.Sprintf("unhandled infection type %v", state[current]))
+		}
+		// move forward
+		current = [2]int{current[0] + dirs[dirIndex][0], current[1] + dirs[dirIndex][1]}
+	}
+
+	return countBursts
+}
+
+var dirs = [][2]int{
+	{-1, 0}, // up
+	{0, 1},  // right
+	{1, 0},  // down
+	{0, -1}, // left
+}
+
+type infectedState int
+
+const (
+	clean infectedState = iota
+	weakened
+	infected
+	flagged
+)
+
+// this probably makes some cool visuals if a 2D slice is used... but this is easier
+func newStateFromInput(input string) map[[2]int]infectedState {
+	ans := map[[2]int]infectedState{}
+	for r, line := range strings.Split(input, "\n") {
+		for c, v := range strings.Split(line, "") {
+			if v == "#" {
+				ans[[2]int{r, c}] = infected
+			} else if v == "." {
+				ans[[2]int{r, c}] = clean
+			}
+		}
+	}
+	return ans
+}

2017/day22/main_test.go

@@ -0,0 +1,47 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+var example = `..#
+#..
+...`
+
+func Test_part1(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  int
+	}{
+		{"example", example, 5587},
+		{"actual", util.ReadFile("input.txt"), 5575},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := part1(tt.input); got != tt.want {
+				t.Errorf("part1() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_part2(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  int
+	}{
+		{"example", example, 2511944},
+		{"actual", util.ReadFile("input.txt"), 2511991},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := part2(tt.input); got != tt.want {
+				t.Errorf("part2() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}