day18

day18p1/solution.go

@@ -0,0 +1,82 @@
+package day18p1
+
+import (
+	"fmt"
+	"io"
+
+	"aoc/utils"
+)
+
+func Solve(r io.Reader) any {
+	lines := utils.ReadLines(r)
+
+	isTest := len(lines) < 30
+
+	numSimulated := 12
+	if !isTest {
+		numSimulated = 1024
+	}
+	size := 6
+	if !isTest {
+		size = 70
+	}
+
+	corrupted := make(map[utils.Point]bool)
+	bytes := make([]utils.Point, 0)
+	for _, line := range lines {
+		x, y := 0, 0
+		fmt.Sscanf(line, "%d,%d", &x, &y)
+		bytes = append(bytes, utils.Point{X: x, Y: y})
+	}
+	for i := 0; i < numSimulated; i++ {
+		corrupted[bytes[i]] = true
+	}
+
+	return steps(corrupted, size)
+}
+
+func steps(corrupted map[utils.Point]bool, size int) int {
+	type state struct {
+		pos   utils.Point
+		steps int
+	}
+	queue := make([]state, 0)
+	visited := make(map[utils.Point]bool)
+	end := utils.Point{X: size, Y: size}
+	var enqueue = func(p utils.Point, s int) {
+		for i := 0; i < len(queue); i++ {
+			if queue[i].steps > s {
+				queue = append(queue[:i], append([]state{{pos: p, steps: s}}, queue[i:]...)...)
+				return
+			}
+		}
+		queue = append(queue, state{pos: p, steps: s})
+	}
+	var dequeue = func() state {
+		current := queue[0]
+		queue = queue[1:]
+		return current
+	}
+	enqueue(utils.Point{X: 0, Y: 0}, 0)
+	for len(queue) > 0 {
+		current := dequeue()
+		if current.pos == end {
+			return current.steps
+		}
+		if visited[current.pos] {
+			continue
+		}
+		visited[current.pos] = true
+		for _, dir := range utils.Directions {
+			next := current.pos.Add(dir)
+			if next.X < 0 || next.Y < 0 || next.X > size || next.Y > size {
+				continue
+			}
+			if corrupted[next] {
+				continue
+			}
+			enqueue(next, current.steps+1)
+		}
+	}
+	return -1
+}

day18p1/solution_test.go

@@ -0,0 +1,57 @@
+package day18p1
+
+import (
+	"strings"
+	"testing"
+
+	"aoc/utils"
+)
+
+var testInput = `5,4
+4,2
+4,5
+3,0
+2,1
+6,3
+2,4
+1,5
+0,6
+3,3
+2,6
+5,1
+1,2
+5,5
+2,5
+6,5
+1,4
+0,4
+6,4
+1,1
+6,1
+1,0
+0,5
+1,6
+2,0`
+
+func TestSolve(t *testing.T) {
+	tests := []struct {
+		input  string
+		answer int
+	}{
+		{testInput, 22},
+	}
+
+	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)
+		}
+	}
+}

day18p2/solution.go

@@ -0,0 +1,89 @@
+package day18p2
+
+import (
+	"fmt"
+	"io"
+	"strconv"
+
+	"aoc/utils"
+)
+
+func Solve(r io.Reader) any {
+	lines := utils.ReadLines(r)
+
+	isTest := len(lines) < 30
+
+	numSimulated := 12
+	if !isTest {
+		numSimulated = 1024
+	}
+	size := 6
+	if !isTest {
+		size = 70
+	}
+
+	corrupted := make(map[utils.Point]bool)
+	bytes := make([]utils.Point, 0)
+	for _, line := range lines {
+		x, y := 0, 0
+		fmt.Sscanf(line, "%d,%d", &x, &y)
+		bytes = append(bytes, utils.Point{X: x, Y: y})
+	}
+	for i := 0; i < numSimulated; i++ {
+		corrupted[bytes[i]] = true
+	}
+	for i := size; i < len(bytes); i++ {
+		corrupted[bytes[i]] = true
+		if steps(corrupted, size) == -1 {
+			return strconv.Itoa(bytes[i].X) + "," + strconv.Itoa(bytes[i].Y)
+		}
+	}
+
+	return ""
+}
+
+func steps(corrupted map[utils.Point]bool, size int) int {
+	type state struct {
+		pos   utils.Point
+		steps int
+	}
+	queue := make([]state, 0)
+	visited := make(map[utils.Point]bool)
+	end := utils.Point{X: size, Y: size}
+	var enqueue = func(p utils.Point, s int) {
+		for i := 0; i < len(queue); i++ {
+			if queue[i].steps > s {
+				queue = append(queue[:i], append([]state{{pos: p, steps: s}}, queue[i:]...)...)
+				return
+			}
+		}
+		queue = append(queue, state{pos: p, steps: s})
+	}
+	var dequeue = func() state {
+		current := queue[0]
+		queue = queue[1:]
+		return current
+	}
+	enqueue(utils.Point{X: 0, Y: 0}, 0)
+	for len(queue) > 0 {
+		current := dequeue()
+		if current.pos == end {
+			return current.steps
+		}
+		if visited[current.pos] {
+			continue
+		}
+		visited[current.pos] = true
+		for _, dir := range utils.Directions {
+			next := current.pos.Add(dir)
+			if next.X < 0 || next.Y < 0 || next.X > size || next.Y > size {
+				continue
+			}
+			if corrupted[next] {
+				continue
+			}
+			enqueue(next, current.steps+1)
+		}
+	}
+	return -1
+}

day18p2/solution_test.go

@@ -0,0 +1,57 @@
+package day18p2
+
+import (
+	"strings"
+	"testing"
+
+	"aoc/utils"
+)
+
+var testInput = `5,4
+4,2
+4,5
+3,0
+2,1
+6,3
+2,4
+1,5
+0,6
+3,3
+2,6
+5,1
+1,2
+5,5
+2,5
+6,5
+1,4
+0,4
+6,4
+1,1
+6,1
+1,0
+0,5
+1,6
+2,0`
+
+func TestSolve(t *testing.T) {
+	tests := []struct {
+		input  string
+		answer string
+	}{
+		{testInput, "6,1"},
+	}
+
+	if testing.Verbose() {
+		utils.Verbose = true
+	}
+
+	for _, test := range tests {
+		r := strings.NewReader(test.input)
+
+		result := Solve(r).(string)
+
+		if result != test.answer {
+			t.Errorf("Expected %s, got %s", test.answer, result)
+		}
+	}
+}