Implementation for 15b

challenge/day15/b.go

@@ -0,0 +1,56 @@
+package day15
+
+import (
+	"fmt"
+
+	"github.com/nlowe/aoc2019/challenge"
+	"github.com/spf13/cobra"
+)
+
+var B = &cobra.Command{
+	Use:   "15b",
+	Short: "Day 15, Problem B",
+	Run: func(_ *cobra.Command, _ []string) {
+		fmt.Printf("Answer: %d\n", b(challenge.FromFile()))
+	},
+}
+
+func b(challenge *challenge.Input) int {
+	s, _, _ := mapShip(challenge)
+
+	m := 0
+	for tryFill(s) {
+		m++
+	}
+
+	return m
+}
+
+func tryFill(s *ship) bool {
+	var toFill []*tile
+	s.each(func(t *tile) {
+		if t.t != statusOxygenSystemFound {
+			return
+		}
+
+		for _, delta := range []struct {
+			x int
+			y int
+		}{
+			{-1, 0},
+			{1, 0},
+			{0, -1},
+			{0, 1},
+		} {
+			if candidate := s.tileAt(t.x+delta.x, t.y+delta.y); candidate != nil && candidate.t == statusOk {
+				toFill = append(toFill, candidate)
+			}
+		}
+	})
+
+	for _, t := range toFill {
+		t.t = statusOxygenSystemFound
+	}
+
+	return len(toFill) > 0
+}

challenge/day15/ship.go

@@ -83,3 +83,11 @@ func (s *ship) tileAt(x, y int) *tile {
 
 	return s.m[x][y]
 }
+
+func (s *ship) each(f func(t *tile)) {
+	for _, r := range s.m {
+		for _, t := range r {
+			f(t)
+		}
+	}
+}

main.go

@@ -73,7 +73,7 @@ func init() {
 		day12.A, day12.B,
 		day13.A, day13.B,
 		day14.A, day14.B,
-		day15.A,
+		day15.A, day15.B,
 	)
 
 	flags := rootCmd.PersistentFlags()