finished day 21 part 1

.gitignore

@@ -5,3 +5,4 @@
 run.go
 aoc_run
 day20p2/relations.gv
+day20p2/relations.pdf

day21p1/solution.go

@@ -0,0 +1,72 @@
+package day21p1
+
+import (
+	"io"
+
+	"aoc/utils"
+)
+
+func Solve(r io.Reader) any {
+	return solveSteps(r, 64)
+}
+
+func solveSteps(r io.Reader, steps int) int {
+	lines := utils.ReadLines(r)
+
+	garden := Maze{make(map[utils.Point]rune), utils.NewBFS[utils.Point](), steps}
+
+	for j, ln := range lines {
+		for i, r := range ln {
+			p := utils.Point{X: i, Y: -j}
+			garden.positions[p] = r
+		}
+	}
+
+	_, err := garden.bfs.Run(garden)
+	if err != utils.BFSNotFound {
+		panic("this should end when points are exhausted")
+	}
+
+	count := 0
+	for _, d := range garden.bfs.Distance {
+		if d%2 == 0 {
+			count++
+		}
+	}
+
+	return count
+}
+
+type Maze struct {
+	positions map[utils.Point]rune
+	bfs       *utils.BreadthFirstSearch[utils.Point]
+	steps     int
+}
+
+func (m Maze) GetInitial() utils.Point {
+	for k, v := range m.positions {
+		if v == 'S' {
+			return k
+		}
+	}
+	panic("unable to find starting point")
+}
+
+func (m Maze) GetNeighbors(pos utils.Point) []utils.Point {
+	ret := []utils.Point{}
+
+	if m.bfs.Distance[pos] < uint64(m.steps) {
+		for _, dir := range utils.Directions {
+			np := pos.Add(dir)
+			if m.positions[np] == '.' {
+				ret = append(ret, np)
+			}
+		}
+	}
+
+	return ret
+}
+
+func (m Maze) IsFinal(pos utils.Point) bool {
+	return false
+}

day21p1/solution_test.go

@@ -0,0 +1,43 @@
+package day21p1
+
+import (
+	"strings"
+	"testing"
+
+	"aoc/utils"
+)
+
+var testInput = `...........
+.....###.#.
+.###.##..#.
+..#.#...#..
+....#.#....
+.##..S####.
+.##..#...#.
+.......##..
+.##.#.####.
+.##..##.##.
+...........`
+
+func TestSolve(t *testing.T) {
+	tests := []struct {
+		input  string
+		answer int
+	}{
+		{testInput, 16},
+	}
+
+	if testing.Verbose() {
+		utils.Verbose = true
+	}
+
+	for _, test := range tests {
+		r := strings.NewReader(test.input)
+
+		result := solveSteps(r, 6)
+
+		if result != test.answer {
+			t.Errorf("Expected %d, got %d", test.answer, result)
+		}
+	}
+}