add day-15 part1

day-15/internal/one/direction.go

@@ -0,0 +1,16 @@
+package one
+
+import "slices"
+
+type direction int
+
+const (
+	N direction = iota
+	E
+	S
+	W
+)
+
+func directions(dir rune) direction {
+	return direction(slices.Index([]rune{'^', '>', 'v', '<'}, dir))
+}

day-15/internal/one/graph.go

@@ -0,0 +1,50 @@
+package one
+
+import (
+	"strings"
+)
+
+type graph struct {
+	robot point
+	boxes map[point]struct{}
+	data  []string
+}
+
+func newGraph() *graph {
+	return &graph{boxes: make(map[point]struct{})}
+}
+
+func (g *graph) String() string {
+	return strings.Join(g.data, "\n")
+}
+
+func (g *graph) valueAt(point point) rune {
+	return rune(g.data[point.y][point.x])
+}
+
+func (g *graph) updateRobot(dir direction) {
+	new := neighbours(g.robot)[dir]
+
+	g.updateEach(g.robot, '.')
+	g.updateEach(new, '@')
+	g.robot = new
+}
+
+func (g *graph) updateBox(point point, dir direction) {
+	g.deleteBox(point)
+	g.addBox(neighbours(point)[dir])
+}
+
+func (g *graph) deleteBox(point point) {
+	delete(g.boxes, point)
+	g.updateEach(point, '.')
+}
+
+func (g *graph) addBox(point point) {
+	g.boxes[point] = struct{}{}
+	g.updateEach(point, 'O')
+}
+
+func (g *graph) updateEach(point point, r rune) {
+	g.data[point.y] = replaceAtIndex(g.data[point.y], r, point.x)
+}

day-15/internal/one/neighbours.go

@@ -0,0 +1,10 @@
+package one
+
+func neighbours(p point) [4]point {
+	return [4]point{
+		{p.x, p.y - 1}, // N
+		{p.x + 1, p.y}, // E
+		{p.x, p.y + 1}, // S
+		{p.x - 1, p.y}, // W
+	}
+}

day-15/internal/one/point.go

@@ -0,0 +1,10 @@
+package one
+
+type point struct {
+	x int
+	y int
+}
+
+func newPoint(x, y int) point {
+	return point{x, y}
+}

day-15/internal/one/solve.go

@@ -0,0 +1,57 @@
+package one
+
+import (
+	"bytes"
+
+	log "github.com/sirupsen/logrus"
+)
+
+func Solve(buf []byte) (int, error) {
+	r := bytes.NewReader(buf)
+	graph, dirs, err := parseLines(r)
+	if err != nil {
+		return 0, err
+	}
+
+	for _, dir := range dirs {
+		log.Debugf("about to explore '%s' direction from robot location %v", string(dir), graph.robot)
+
+		stack, ok := explore(graph, graph.robot, directions(dir), newStack())
+		if !ok {
+			log.Debug("path ends with '#', continuing...")
+			continue
+		}
+
+		for !stack.IsEmpty() {
+			point := stack.Pop().(point)
+			graph.updateBox(point, directions(dir))
+		}
+		graph.updateRobot(directions(dir))
+
+		log.Debugf("\n%s\n", graph.String())
+	}
+
+	var sum int
+	for box := range graph.boxes {
+		sum += (100 * box.y) + box.x
+	}
+
+	return sum, nil
+}
+
+func explore(graph *graph, next point, direction direction, stack *stack) (*stack, bool) {
+	ns := neighbours(next)
+
+	log.Debug(string(graph.valueAt(ns[direction])))
+
+	switch graph.valueAt(ns[direction]) {
+	case '#':
+		return nil, false
+	case '.':
+		return stack, true
+	case 'O':
+		stack.Push(ns[direction])
+	}
+
+	return explore(graph, ns[direction], direction, stack)
+}

day-15/internal/one/solve_internal_test.go

@@ -0,0 +1,15 @@
+package one
+
+import (
+	_ "embed"
+	"os"
+	"testing"
+)
+
+//go:embed testdata/input.txt
+var data []byte
+
+func BenchmarkSolve(b *testing.B) {
+	os.Stdout, _ = os.Open(os.DevNull)
+	Solve(data)
+}

day-15/internal/one/stack.go

@@ -0,0 +1,33 @@
+package one
+
+type stack struct {
+	items []interface{}
+}
+
+func newStack() *stack {
+	return &stack{}
+}
+
+func (s *stack) Push(element interface{}) interface{} {
+	s.items = append(s.items, element)
+	return element
+}
+
+func (s *stack) Pop() interface{} {
+	l := len(s.items)
+	element := s.items[l-1]
+	s.items = s.items[:l-1]
+	return element
+}
+
+func (s *stack) Peek() interface{} {
+	return s.items[len(s.items)-1]
+}
+
+func (s *stack) Len() int {
+	return len(s.items)
+}
+
+func (s *stack) IsEmpty() bool {
+	return s.Len() == 0
+}

day-15/internal/one/util.go

@@ -0,0 +1,59 @@
+package one
+
+import (
+	"bufio"
+	"io"
+	"regexp"
+	"strings"
+
+	log "github.com/sirupsen/logrus"
+)
+
+var reBoxes = regexp.MustCompile(`O`)
+
+func parseLines(r io.Reader) (*graph, string, error) {
+	graph := newGraph()
+	var directions []string
+
+	var inDirections bool
+	var linecount int
+	scanner := bufio.NewScanner(r)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if len(line) == 0 {
+			inDirections = true
+			continue
+		}
+
+		matches := reBoxes.FindAllStringIndex(line, -1)
+		for _, m := range matches {
+			graph.boxes[newPoint(m[0], linecount)] = struct{}{}
+		}
+
+		if inDirections {
+			directions = append(directions, line)
+		} else {
+			indx := strings.Index(line, "@")
+			if indx != -1 {
+				log.Debugf("adding start point at (%d, %d)", indx, linecount)
+				graph.robot = newPoint(indx, linecount)
+			}
+
+			graph.data = append(graph.data, line)
+		}
+
+		linecount++
+	}
+
+	if err := scanner.Err(); err != nil {
+		return nil, "", err
+	}
+
+	return graph, strings.Join(directions, ""), nil
+}
+
+func replaceAtIndex(s string, r rune, i int) string {
+	out := []rune(s)
+	out[i] = r
+	return string(out)
+}