refactor: create bfs helper

Author: believer

go/2025/puzzles/day07/main.go

@@ -3,13 +3,14 @@ package main
 import (
 	"fmt"
 
+	"github.com/believer/aoc-utils/algorithms/bfs"
 	"github.com/believer/aoc-utils/files"
 	"github.com/believer/aoc-utils/grid"
 )
 
 // I spent too much time trying to make a flawed solution work.
-// I thought of BFS (I've had it in the back of my mind that
-// it would appear at some point) but kept working on the path I had taken ':D
+// I thought of BFS (I've had it in the back of my mind that it would
+// appear at some point) but kept working on the path I had taken ':D
 // Eventually, I gave up and looked at my solution from day 18 2024 to remember.
 
 func main() {
@@ -22,34 +23,30 @@ func part1(name string) (splits int) {
 	manifold := grid.New(lines)
 	start, _ := manifold.Find('S')
 
-	queue := []grid.Point{start}
-	seen := map[grid.Point]bool{}
+	queue := bfs.New(start)
 
-	for len(queue) > 0 {
-		beam := queue[0]
-		queue = queue[1:]
+	for queue.Loop() {
+		beam := queue.Pop()
 
 		// Keep track of what we've seen since beams
 		// can split into the same position
-		if _, ok := seen[beam]; ok {
+		if queue.HasVisited(beam) {
 			continue
 		}
 
 		if !manifold.InBounds(beam) {
 			continue
 		}
 
-		seen[beam] = true
+		queue.Visit(beam)
 
 		if manifold.Get(beam) == '^' {
 			splits += 1
-			leftSplit := beam.Add(grid.LEFT)
-			rightSplit := beam.Add(grid.RIGHT)
 
-			queue = append(queue, leftSplit)
-			queue = append(queue, rightSplit)
+			queue.Push(beam.Add(grid.LEFT))
+			queue.Push(beam.Add(grid.RIGHT))
 		} else {
-			queue = append(queue, beam.Add(grid.DOWN))
+			queue.Push(beam.Add(grid.DOWN))
 		}
 	}
 

go/utils/algorithms/bfs/bfs.go

@@ -0,0 +1,48 @@
+package bfs
+
+import "github.com/believer/aoc-utils/grid"
+
+type BFS struct {
+	Queue   []grid.Point
+	Visited map[grid.Point]bool
+}
+
+// Start a Breadth-first search (BFS) from a given start point
+func New(start grid.Point) BFS {
+	queue := []grid.Point{start}
+
+	return BFS{
+		Queue:   queue,
+		Visited: map[grid.Point]bool{},
+	}
+}
+
+// Report whether we still have items in the queue
+func (b *BFS) Loop() bool {
+	return len(b.Queue) > 0
+}
+
+// Grab (and remove) the first item in the queue and
+func (b *BFS) Pop() (current grid.Point) {
+	current = b.Queue[0]
+	b.Queue = b.Queue[1:]
+
+	return
+}
+
+// Add a new point to the queue
+func (b *BFS) Push(p grid.Point) {
+	b.Queue = append(b.Queue, p)
+}
+
+// Report whether we've visited a given point
+func (b *BFS) HasVisited(p grid.Point) (ok bool) {
+	_, ok = b.Visited[p]
+
+	return
+}
+
+// Set a point as visited
+func (b *BFS) Visit(p grid.Point) {
+	b.Visited[p] = true
+}