day8 part2

day8/input0.txt

@@ -0,0 +1,20 @@
+162,817,812
+57,618,57
+906,360,560
+592,479,940
+352,342,300
+466,668,158
+542,29,236
+431,825,988
+739,650,466
+52,470,668
+216,146,977
+819,987,18
+117,168,530
+805,96,715
+346,949,466
+970,615,88
+941,993,340
+862,61,35
+984,92,344
+425,690,689

day8/main.go

@@ -0,0 +1,208 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"slices"
+	"strconv"
+	"strings"
+
+	"github.com/dominikbraun/graph"
+)
+
+func readLines(filename string) []string {
+	raw, err := os.ReadFile(filename)
+	if err != nil {
+		panic(err)
+	}
+	return strings.Split(string(raw), "\n")
+}
+
+// input1 80446
+func main() {
+	filename := "input0.txt"
+	if len(os.Args) > 1 {
+		filename = os.Args[1]
+	}
+	lines := readLines(filename)
+	p := parsePlayground(lines)
+	circuits, err := p.wireClosest(1000)
+	if err != nil {
+		panic(err)
+	}
+	counts := map[uint]uint{}
+	for _, circuit := range circuits {
+		counts[circuit]++
+	}
+	totals := []uint{}
+	for _, v := range counts {
+		totals = append(totals, v)
+	}
+	slices.Sort(totals)
+	slices.Reverse(totals)
+	fmt.Printf("%v\n", totals[0]*totals[1]*totals[2])
+	xx, err := p.wireAll()
+	if err != nil {
+		panic(err)
+	}
+	fmt.Printf("%d\n", xx)
+}
+
+func parsePlayground(lines []string) playground {
+	p := playground{
+		boxes:     []box{},
+		distances: graph.New(boxHash, graph.Weighted()),
+	}
+	for _, line := range lines {
+		parts := strings.Split(line, ",")
+		b := box{line: line}
+		b.x, _ = strconv.Atoi(parts[0])
+		b.y, _ = strconv.Atoi(parts[1])
+		b.z, _ = strconv.Atoi(parts[2])
+		_ = p.distances.AddVertex(b)
+		for _, c := range p.boxes {
+			_ = p.distances.AddEdge(b.line, c.line, graph.EdgeWeight(b.distanceTo(c)))
+		}
+		p.boxes = append(p.boxes, b)
+	}
+	return p
+}
+
+func (p *playground) wireClosest(n uint64) (map[string]uint, error) {
+	edges, err := p.distances.Edges()
+	if err != nil {
+		return nil, err
+	}
+	slices.SortFunc(edges, func(e1, e2 graph.Edge[string]) int {
+		return e1.Properties.Weight - e2.Properties.Weight
+	})
+	nextCircuit := uint(1)
+	circuits := map[string]uint{}
+	for i := range n {
+		edge := edges[i]
+		sourceCircuit := circuits[edge.Source]
+		targetCircuit := circuits[edge.Target]
+		if sourceCircuit == 0 && targetCircuit == 0 {
+			circuits[edge.Source] = nextCircuit
+			circuits[edge.Target] = nextCircuit
+			nextCircuit++
+			continue
+		}
+		if sourceCircuit == 0 {
+			circuits[edge.Source] = targetCircuit
+			continue
+		}
+		if targetCircuit == 0 {
+			circuits[edge.Target] = sourceCircuit
+			continue
+		}
+		if sourceCircuit == targetCircuit {
+			continue
+		}
+		for k, v := range circuits {
+			if v == targetCircuit {
+				circuits[k] = sourceCircuit
+			}
+		}
+	}
+	return circuits, nil
+}
+
+func (p *playground) wireAll() (int, error) {
+	edges, err := p.distances.Edges()
+	if err != nil {
+		return 0, err
+	}
+	slices.SortFunc(edges, func(e1, e2 graph.Edge[string]) int {
+		return e1.Properties.Weight - e2.Properties.Weight
+	})
+	circuitsInUse := 0
+	nextCircuit := uint(1)
+	circuits := map[string]uint{}
+	for _, edge := range edges {
+		sourceCircuit := circuits[edge.Source]
+		targetCircuit := circuits[edge.Target]
+		if sourceCircuit == 0 && targetCircuit == 0 {
+			circuits[edge.Source] = nextCircuit
+			circuits[edge.Target] = nextCircuit
+			nextCircuit++
+			circuitsInUse++
+			continue
+		}
+		if sourceCircuit == 0 {
+			circuits[edge.Source] = targetCircuit
+			if circuitsInUse == 1 {
+				count, _ := p.distances.Order()
+				if count == len(circuits) {
+					v1, _ := p.distances.Vertex(edge.Source)
+					v2, _ := p.distances.Vertex(edge.Target)
+					return v1.x * v2.x, nil
+				}
+			}
+			continue
+		}
+		if targetCircuit == 0 {
+			circuits[edge.Target] = sourceCircuit
+			if circuitsInUse == 1 {
+				count, _ := p.distances.Order()
+				if count == len(circuits) {
+					v1, _ := p.distances.Vertex(edge.Source)
+					v2, _ := p.distances.Vertex(edge.Target)
+					return v1.x * v2.x, nil
+				}
+			}
+			continue
+		}
+		if sourceCircuit == targetCircuit {
+			if circuitsInUse == 1 {
+				count, _ := p.distances.Order()
+				if count == len(circuits) {
+					v1, _ := p.distances.Vertex(edge.Source)
+					v2, _ := p.distances.Vertex(edge.Target)
+					return v1.x * v2.x, nil
+				}
+			}
+			continue
+		}
+		for k, v := range circuits {
+			if v == targetCircuit {
+				circuits[k] = sourceCircuit
+			}
+		}
+		circuitsInUse--
+		if circuitsInUse == 1 {
+			count, _ := p.distances.Order()
+			if count == len(circuits) {
+				v1, _ := p.distances.Vertex(edge.Source)
+				v2, _ := p.distances.Vertex(edge.Target)
+				return v1.x * v2.x, nil
+			}
+		}
+	}
+	v, _ := p.distances.Order()
+	return 0, fmt.Errorf("exhausted edges without reaching full connectivity %v", v)
+}
+
+type playground struct {
+	boxes     []box
+	distances graph.Graph[string, box]
+}
+
+func boxHash(b box) string {
+	return b.line
+}
+
+type box struct {
+	line string
+	x    int
+	y    int
+	z    int
+}
+
+func (b box) distanceTo(c box) int {
+	x := c.x - b.x
+	y := c.y - b.y
+	z := c.z - b.z
+	// no need to sqrt since we only care about relative distances
+	return x*x + y*y + z*z
+}

go.mod

@@ -3,6 +3,7 @@ module ballstads.name/aoc2025
 go 1.25.5
 
 require (
+	github.com/dominikbraun/graph v0.23.0 // indirect
 	github.com/kelindar/bitmap v1.5.3 // indirect
 	github.com/kelindar/simd v1.1.2 // indirect
 	github.com/klauspost/cpuid/v2 v2.2.4 // indirect

go.sum

@@ -1,3 +1,5 @@
+github.com/dominikbraun/graph v0.23.0 h1:TdZB4pPqCLFxYhdyMFb1TBdFxp8XLcJfTTBQucVPgCo=
+github.com/dominikbraun/graph v0.23.0/go.mod h1:yOjYyogZLY1LSG9E33JWZJiq5k83Qy2C6POAuiViluc=
 github.com/kelindar/bitmap v1.5.3 h1:/ty1SvbLE5ZKO4ToFNeXe3P3RrQsoj4a0x5gZNp5Vzo=
 github.com/kelindar/bitmap v1.5.3/go.mod h1:j3qZjxH9s4OtvsnFTP2bmPkjqil9Y2xQlxPYHexasEA=
 github.com/kelindar/simd v1.1.2 h1:KduKb+M9cMY2HIH8S/cdJyD+5n5EGgq+Aeeleos55To=