day8

day08p1/solution.go

@@ -0,0 +1,48 @@
+package day08p1
+
+import (
+	"io"
+
+	"aoc/utils"
+)
+
+type position struct {
+	x, y int
+}
+
+func Solve(r io.Reader) any {
+	lines := utils.ReadLines(r)
+
+	antennaPositions := make(map[rune][]position)
+	antinodes := make(map[position]bool)
+	for i, line := range lines {
+		for j, c := range line {
+			if c == '.' {
+				continue
+			}
+			antennaPositions[c] = append(antennaPositions[c], position{j, i})
+		}
+	}
+	findAntinodes(antennaPositions, antinodes, 1, len(lines), len(lines[0]))
+
+	return len(antinodes)
+}
+
+func findAntinodes(antennaPositions map[rune][]position, antinodes map[position]bool, distance int, rows, cols int) int {
+	prevLen := len(antinodes)
+	for _, aps := range antennaPositions {
+		for i := 0; i < len(aps)-1; i++ {
+			for j := i + 1; j < len(aps); j++ {
+				antinode(rows, cols, position{aps[i].y - distance*(aps[j].y-aps[i].y), aps[i].x - distance*(aps[j].x-aps[i].x)}, antinodes)
+				antinode(rows, cols, position{aps[j].y - distance*(aps[i].y-aps[j].y), aps[j].x - distance*(aps[i].x-aps[j].x)}, antinodes)
+			}
+		}
+	}
+	return len(antinodes) - prevLen
+}
+
+func antinode(rows, cols int, position position, antinodes map[position]bool) {
+	if position.x >= 0 && position.x < rows && position.y >= 0 && position.y < cols {
+		antinodes[position] = true
+	}
+}

day08p1/solution_test.go

@@ -0,0 +1,44 @@
+package day08p1
+
+import (
+	"strings"
+	"testing"
+
+	"aoc/utils"
+)
+
+var testInput = `............
+........0...
+.....0......
+.......0....
+....0.......
+......A.....
+............
+............
+........A...
+.........A..
+............
+............`
+
+func TestSolve(t *testing.T) {
+	tests := []struct {
+		input  string
+		answer int
+	}{
+		{testInput, 14},
+	}
+
+	if testing.Verbose() {
+		utils.Verbose = true
+	}
+
+	for _, test := range tests {
+		r := strings.NewReader(test.input)
+
+		result := Solve(r).(int)
+
+		if result != test.answer {
+			t.Errorf("Expected %d, got %d", test.answer, result)
+		}
+	}
+}

day08p2/solution.go

@@ -0,0 +1,50 @@
+package day08p2
+
+import (
+	"io"
+
+	"aoc/utils"
+)
+
+type position struct {
+	x, y int
+}
+
+func Solve(r io.Reader) any {
+	lines := utils.ReadLines(r)
+
+	antennaPositions := make(map[rune][]position)
+	antinodes := make(map[position]bool)
+	for i, line := range lines {
+		for j, c := range line {
+			if c == '.' {
+				continue
+			}
+			antennaPositions[c] = append(antennaPositions[c], position{j, i})
+		}
+	}
+
+	for distance := 0; findAntinodes(antennaPositions, antinodes, distance, len(lines), len(lines[0])) > 0; distance++ {
+	}
+
+	return len(antinodes)
+}
+
+func findAntinodes(antennaPositions map[rune][]position, antinodes map[position]bool, distance int, rows, cols int) int {
+	prevLen := len(antinodes)
+	for _, aps := range antennaPositions {
+		for i := 0; i < len(aps)-1; i++ {
+			for j := i + 1; j < len(aps); j++ {
+				antinode(rows, cols, position{aps[i].y - distance*(aps[j].y-aps[i].y), aps[i].x - distance*(aps[j].x-aps[i].x)}, antinodes)
+				antinode(rows, cols, position{aps[j].y - distance*(aps[i].y-aps[j].y), aps[j].x - distance*(aps[i].x-aps[j].x)}, antinodes)
+			}
+		}
+	}
+	return len(antinodes) - prevLen
+}
+
+func antinode(rows, cols int, position position, antinodes map[position]bool) {
+	if position.x >= 0 && position.x < rows && position.y >= 0 && position.y < cols {
+		antinodes[position] = true
+	}
+}

day08p2/solution_test.go

@@ -0,0 +1,44 @@
+package day08p2
+
+import (
+	"strings"
+	"testing"
+
+	"aoc/utils"
+)
+
+var testInput = `............
+........0...
+.....0......
+.......0....
+....0.......
+......A.....
+............
+............
+........A...
+.........A..
+............
+............`
+
+func TestSolve(t *testing.T) {
+	tests := []struct {
+		input  string
+		answer int
+	}{
+		{testInput, 34},
+	}
+
+	if testing.Verbose() {
+		utils.Verbose = true
+	}
+
+	for _, test := range tests {
+		r := strings.NewReader(test.input)
+
+		result := Solve(r).(int)
+
+		if result != test.answer {
+			t.Errorf("Expected %d, got %d", test.answer, result)
+		}
+	}
+}