Day 6 solution

I'm reasonably happy with this. I started with a bi-directional linked list, but realized that a flat list of all nodes came in handy for one use case while the linked list came in handy for another, so I settled on that.

days/06.go

@@ -0,0 +1,114 @@
+package days
+
+import (
+	"fmt"
+	"strings"
+
+	"parnic.com/aoc2019/utilities"
+)
+
+type body struct {
+	orbits *body
+	obj    string
+}
+
+type Day06 struct {
+	allBodies []*body
+}
+
+func (d *Day06) Parse() {
+	d.allBodies = make([]*body, 0)
+
+	getOrAddBody := func(obj string) *body {
+		target := d.findBody(obj)
+		if target == nil {
+			target = &body{
+				obj: obj,
+			}
+			d.allBodies = append(d.allBodies, target)
+		}
+
+		return target
+	}
+
+	lines := utilities.GetStringLines("06p")
+	for _, line := range lines {
+		bodies := strings.Split(line, ")")
+		newBody := getOrAddBody(bodies[1])
+
+		target := getOrAddBody(bodies[0])
+		newBody.orbits = target
+	}
+}
+
+func (d *Day06) findBody(obj string) *body {
+	for _, checkBody := range d.allBodies {
+		if checkBody.obj == obj {
+			return checkBody
+		}
+	}
+
+	return nil
+}
+
+func (d Day06) Num() int {
+	return 6
+}
+
+func (d *Day06) Part1() string {
+	orbits := 0
+	for _, obj := range d.allBodies {
+		next := obj.orbits
+		for next != nil {
+			next = next.orbits
+			orbits++
+		}
+	}
+
+	return fmt.Sprintf("Total orbits: %s%d%s", utilities.TextBold, orbits, utilities.TextReset)
+}
+
+func (d *Day06) Part2() string {
+	you := d.findBody("YOU")
+	san := d.findBody("SAN")
+
+	youChildren := make([]*body, 0)
+	next := you.orbits
+	for next != nil {
+		youChildren = append(youChildren, next)
+		next = next.orbits
+	}
+
+	var linkingNode *body
+	next = san.orbits
+	for next != nil {
+		if utilities.ArrayContains(youChildren, next) {
+			linkingNode = next
+			break
+		}
+		next = next.orbits
+	}
+
+	if linkingNode == nil {
+		panic("")
+	}
+
+	getDistToLinking := func(start *body) int {
+		dist := 0
+		next = start.orbits
+		for next != nil {
+			if next == linkingNode {
+				break
+			}
+			dist++
+			next = next.orbits
+		}
+
+		return dist
+	}
+
+	distYouToLinking := getDistToLinking(you)
+	distSanToLinking := getDistToLinking(san)
+
+	return fmt.Sprintf("Transfers to get to Santa: %s%d%s", utilities.TextBold, distYouToLinking+distSanToLinking, utilities.TextReset)
+}

inputs/06s1.txt

@@ -0,0 +1,11 @@
+COM)B
+B)C
+C)D
+D)E
+E)F
+B)G
+G)H
+D)I
+E)J
+J)K
+K)L

inputs/06s2.txt

@@ -0,0 +1,13 @@
+COM)B
+B)C
+C)D
+D)E
+E)F
+B)G
+G)H
+D)I
+E)J
+J)K
+K)L
+K)YOU
+I)SAN

main.go

@@ -36,6 +36,7 @@ var dayMap = []day{
 	&days.Day03{},
 	&days.Day04{},
 	&days.Day05{},
+	&days.Day06{},
 }
 
 func main() {

utilities/array.go

@@ -0,0 +1,12 @@
+package utilities
+
+// ArrayContains returns whether the specified array contains the specified value
+func ArrayContains[T comparable](array []T, val T) bool {
+	for _, v := range array {
+		if v == val {
+			return true
+		}
+	}
+
+	return false
+}