day23, part1

day23/aLongWalk.go

@@ -0,0 +1,22 @@
+package day23
+
+import (
+	"fmt"
+)
+
+// length of longest scenic route
+func Run() int {
+	fmt.Println("day 23")
+	filename := "day23/example"
+	field := ReadField(filename)
+	finalPaths := RunAllScenicPaths(field)
+
+	max := 0
+	for _, path := range finalPaths {
+		if path.visited.Cardinality() > max {
+			max = path.visited.Cardinality()
+		}
+	}
+	return max
+}
+

day23/example

@@ -0,0 +1,23 @@
+#.#####################
+#.......#########...###
+#######.#########.#.###
+###.....#.>.>.###.#.###
+###v#####.#v#.###.#.###
+###.>...#.#.#.....#...#
+###v###.#.#.#########.#
+###...#.#.#.......#...#
+#####.#.#.#######.#.###
+#.....#.#.#.......#...#
+#.#####.#.#.#########v#
+#.#...#...#...###...>.#
+#.#.#v#######v###.###v#
+#...#.>.#...>.>.#.###.#
+#####v#.#.###v#.#.###.#
+#.....#...#...#.#.#...#
+#.#########.###.#.#.###
+#...###...#...#...#.###
+###.###.#.###v#####v###
+#...#...#.#.>.>.#.>.###
+#.###.###.#.###.#.#v###
+#.....###...###...#...#
+#####################.#

day23/field.go

@@ -0,0 +1,112 @@
+package day23
+
+import (
+	"fmt"
+	"os"
+	"strings"
+)
+
+type Coord struct {
+	Row, Col int
+}
+
+type CellType rune
+
+const (
+	Path       CellType = '.'
+	Tree       CellType = '#'
+	SlideDown  CellType = 'v'
+	SlideUp    CellType = '^'
+	SlideLeft  CellType = '<'
+	SlideRight CellType = '>'
+)
+
+type Field struct {
+	MaxRow, MaxCol   int
+	Cells            map[Coord]CellType
+	StartCol, EndCol int
+}
+
+func (f *Field) Neighbors(c Coord) (neighbors []Coord) {
+	symb, exists := f.Cells[c]
+	if !exists {
+		panic(fmt.Sprintf("coord %+v not found in field", c))
+	}
+
+	var coords []Coord
+	switch symb {
+	case Path:
+		coords = []Coord{
+			{Row: c.Row + 1, Col: c.Col},
+			{Row: c.Row - 1, Col: c.Col},
+			{Row: c.Row, Col: c.Col + 1},
+			{Row: c.Row, Col: c.Col - 1},
+		}
+	case Tree:
+		panic(fmt.Sprintf("attempting to get neighbors of a tree at %+v", c))
+	case SlideDown:
+		coords = []Coord{{Row: c.Row + 1, Col: c.Col}}
+	case SlideUp:
+		coords = []Coord{{Row: c.Row - 1, Col: c.Col}}
+	case SlideLeft:
+		coords = []Coord{{Row: c.Row, Col: c.Col - 1}}
+	case SlideRight:
+		coords = []Coord{{Row: c.Row, Col: c.Col + 1}}
+	}
+
+	for _, coord := range coords {
+		neighborSymb, found := f.Cells[coord]
+		if !found || neighborSymb == Tree {
+			continue
+		}
+		neighbors = append(neighbors, coord)
+	}
+	return
+}
+
+func (f *Field) String() (result string) {
+	result += "\n"
+	for row := 0; row <= f.MaxRow; row++ {
+		for col := 0; col <= f.MaxCol; col++ {
+			if row == 0 && col == f.StartCol {
+				result += "S"
+				continue
+			}
+			if row == f.MaxRow && col == f.EndCol {
+				result += "E"
+				continue
+			}
+
+			symb := f.Cells[Coord{Row: row, Col: col}]
+			result += string(symb)
+		}
+		result += "\n"
+	}
+	return
+}
+
+func ReadField(filename string) (result Field) {
+	bytes, err := os.ReadFile(filename)
+	if err != nil {
+		panic(err)
+	}
+	lines := strings.Split(strings.TrimSpace(string(bytes)), "\n")
+	result.MaxRow = len(lines) - 1
+	result.MaxCol = len(lines[0]) - 1
+	rows := make(map[Coord]CellType)
+
+	for rowNum, row := range lines {
+		for colNum, symb := range row {
+			rows[Coord{Row: rowNum, Col: colNum}] = CellType(symb)
+			if rowNum == 0 && symb == rune(Path) {
+				result.StartCol = colNum
+			}
+			if rowNum == result.MaxRow && symb == rune(Path) {
+				result.EndCol = colNum
+			}
+		}
+	}
+	result.Cells = rows
+
+	return
+}

day23/field_test.go

@@ -0,0 +1,31 @@
+package day23
+
+import "testing"
+
+func TestReadField(t *testing.T) {
+	filename := "example"
+	field := ReadField(filename)
+	t.Log(field.String())
+}
+
+func TestStartNeighbors(t *testing.T) {
+	filename := "example"
+	field := ReadField(filename)
+	startNeighbors := field.Neighbors(Coord{Row: 0, Col: field.StartCol})
+	t.Log(startNeighbors)
+}
+
+// 5,3
+func TestForkNeighbors(t *testing.T) {
+	filename := "example"
+	field := ReadField(filename)
+	startNeighbors := field.Neighbors(Coord{Row: 5, Col: 3})
+	t.Log(startNeighbors)
+}
+
+func TestSlideNeighbors(t *testing.T) {
+	filename := "example"
+	field := ReadField(filename)
+	startNeighbors := field.Neighbors(Coord{Row: 6, Col: 3})
+	t.Log(startNeighbors)
+}

day23/paths.go

@@ -0,0 +1,57 @@
+package day23
+
+import (
+	mapset "github.com/deckarep/golang-set/v2"
+)
+
+type PathEnd struct {
+	end     Coord
+	visited mapset.Set[Coord]
+}
+
+func ExtendPath(p PathEnd, f Field) (nextPaths []PathEnd) {
+	endPointNeighbors := f.Neighbors(p.end)
+	for _, potentialNewEnd := range endPointNeighbors {
+		if !p.visited.Contains(potentialNewEnd) {
+			nextVisited := p.visited.Clone()
+			nextVisited.Add(p.end)
+			nextPaths = append(nextPaths, PathEnd{
+				end:     potentialNewEnd,
+				visited: nextVisited,
+			})
+		}
+	}
+
+	return
+}
+
+// return paths that end on End
+func RunAllScenicPaths(f Field) (result []PathEnd) {
+	pathsToFurther := []PathEnd{
+		{end: Coord{Row: 0, Col: f.StartCol}, visited: mapset.NewSet[Coord]()},
+	}
+
+	theEndCoord := Coord{Row: f.MaxRow, Col: f.EndCol}
+
+	for len(pathsToFurther) > 0 {
+		curCheckedPath := pathsToFurther[0]
+		pathsToFurther = pathsToFurther[1:]
+
+		if curCheckedPath.end == theEndCoord {
+			result = append(result, curCheckedPath)
+			continue
+		}
+
+		nextSteps := ExtendPath(curCheckedPath, f)
+
+		// log.Printf("for %+v next steps %+v\n", curCheckedPath, pathsToFurther)
+		// log.Printf("remaining paths to check len is %d", len(pathsToFurther))
+		// log.Println(pathsToFurther)
+
+		if len(nextSteps) > 0 {
+			pathsToFurther = append(pathsToFurther, nextSteps...)
+		}
+	}
+
+	return
+}

day23/paths_test.go

@@ -0,0 +1,19 @@
+package day23
+
+import "testing"
+
+func TestRunAllPaths(t *testing.T) {
+	filename := "example"
+	field := ReadField(filename)
+	finalPaths := RunAllScenicPaths(field)
+	t.Log(finalPaths)
+
+	max := 0
+	for _, path := range finalPaths {
+		if path.visited.Cardinality() > max {
+			max = path.visited.Cardinality()
+		}
+	}
+	t.Logf("max path len is %d", max)
+
+}

main.go

@@ -4,15 +4,15 @@ import (
 	"log"
 	"time"
 
-	"sunshine.industries/aoc2023/day22"
+	"sunshine.industries/aoc2023/day23"
 )
 
 func main() {
 	startTime := time.Now()
 	log.Print("> starting run:")
 
-	result := day22.Run()
+	result := day23.Run()
-	log.Printf("\n\nday22 result: %d\n****\n", result)
+	log.Printf("\n\nday23 result: %d\n****\n", result)
 	endTime := time.Now()
 	diff := endTime.Sub(startTime)
 	log.Printf("execution took %s", diff.String())