2016-day13: bfs a grid with some extra math equation

2016/day13/main.go

@@ -0,0 +1,87 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+
+	"github.com/alexchao26/advent-of-code-go/cast"
+	"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)
+
+	ans := bfs(util.ReadFile("./input.txt"), [2]int{31, 39}, part)
+	fmt.Println("Output:", ans)
+}
+
+var dirs = [][2]int{
+	{-1, 0},
+	{1, 0},
+	{0, 1},
+	{0, -1},
+}
+
+func bfs(input string, destination [2]int, part int) int {
+	inputNum := cast.ToInt(input)
+
+	// bfs queue
+	queue := [][3]int{[3]int{1, 1, 0}} // x,y, DIST
+	// to not re-visit cells
+	visited := map[[2]int]bool{}
+
+	// for part 2
+	uniqueVisitsUnder50 := map[[2]int]bool{}
+
+	for len(queue) > 0 {
+		front := queue[0]
+		queue = queue[1:]
+
+		currentX, currentY := front[0], front[1]
+		currentDist := front[2]
+
+		// part 1 return
+		if part == 1 && currentX == destination[0] && currentY == destination[1] {
+			return currentDist
+		}
+		// if already visited, skip
+		if !visited[[2]int{currentX, currentY}] {
+			// for part 2, check if distance is 50 or less
+			if currentDist <= 50 {
+				uniqueVisitsUnder50[[2]int{currentX, currentY}] = true
+			}
+
+			if part == 2 && currentDist > 50 {
+				break
+			}
+
+			for _, diff := range dirs {
+				nextX, nextY := currentX+diff[0], currentY+diff[1]
+				if nextX >= 0 && nextY >= 0 {
+					if isOpenSpace(nextX, nextY, inputNum) {
+						queue = append(queue, [3]int{nextX, nextY, currentDist + 1})
+					}
+				}
+			}
+		}
+		visited[[2]int{currentX, currentY}] = true
+	}
+
+	return len(uniqueVisitsUnder50)
+}
+
+func isOpenSpace(x, y, inputNum int) bool {
+	num := x*x + 3*x + 2*x*y + y + y*y + inputNum
+	binStr := fmt.Sprintf("%b", num)
+	var ones int
+	for _, char := range binStr {
+		if char == '1' {
+			ones++
+		}
+	}
+
+	return ones%2 == 0
+}

2016/day13/main_test.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+func Test_bfs(t *testing.T) {
+	type args struct {
+		input       string
+		destination [2]int
+		part        int
+	}
+	tests := []struct {
+		name string
+		args args
+		want int
+	}{
+		{"example", args{"10", [2]int{7, 4}, 1}, 11},
+		{"actual_part1", args{util.ReadFile("input.txt"), [2]int{31, 39}, 1}, 86},
+		{"actual_part2", args{util.ReadFile("input.txt"), [2]int{31, 39}, 2}, 127},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := bfs(tt.args.input, tt.args.destination, tt.args.part); got != tt.want {
+				t.Errorf("bfs() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}