day23, part1

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
+}