2024 day 8

2024/08/01.go

@@ -0,0 +1,50 @@
+package main
+
+import (
+	"embed"
+
+	"github.com/dbut2/advent-of-code/pkg/harness"
+	"github.com/dbut2/advent-of-code/pkg/sets"
+	"github.com/dbut2/advent-of-code/pkg/space"
+)
+
+func solve(input space.Grid[byte]) int {
+	locations := map[byte][]space.Cell{}
+	for cell, val := range input.Cells() {
+		if *val == '.' {
+			continue
+		}
+		locations[*val] = append(locations[*val], cell)
+	}
+
+	antinodes := sets.Set[space.Cell]{}
+	for _, list := range locations {
+		for i := range list {
+			for j := range list {
+				if i == j {
+					continue
+				}
+
+				next := list[i].Move(diff(list[i], list[j]))
+				if input.Inside(next) {
+					antinodes.Add(next)
+				}
+			}
+		}
+	}
+
+	return len(antinodes)
+}
+
+func diff(a, b space.Cell) space.Direction {
+	return space.Direction{a[0] - b[0], a[1] - b[1]}
+}
+
+func main() {
+	h := harness.New(solve, inputs)
+	h.Expect(1, 14)
+	h.Run()
+}
+
+//go:embed *.txt
+var inputs embed.FS

2024/08/02.go

@@ -0,0 +1,53 @@
+package main
+
+import (
+	"embed"
+
+	"github.com/dbut2/advent-of-code/pkg/harness"
+	"github.com/dbut2/advent-of-code/pkg/sets"
+	"github.com/dbut2/advent-of-code/pkg/space"
+)
+
+func solve(input space.Grid[byte]) int {
+	antinodes := sets.Set[space.Cell]{}
+	locations := map[byte][]space.Cell{}
+	for cell, val := range input.Cells() {
+		if *val == '.' {
+			continue
+		}
+		antinodes.Add(cell)
+		locations[*val] = append(locations[*val], cell)
+	}
+
+	for _, list := range locations {
+		for i := range list {
+			for j := range list {
+				if i == j {
+					continue
+				}
+
+				next := list[i].Move(diff(list[i], list[j]))
+				for input.Inside(next) {
+					antinodes.Add(next)
+					next = next.Move(diff(list[i], list[j]))
+				}
+			}
+		}
+	}
+
+	return len(antinodes)
+}
+
+func diff(a, b space.Cell) space.Direction {
+	return space.Direction{a[0] - b[0], a[1] - b[1]}
+}
+
+func main() {
+	h := harness.New(solve, inputs)
+	h.Expect(2, 9)
+	h.Expect(1, 34)
+	h.Run()
+}
+
+//go:embed *.txt
+var inputs embed.FS