aoc2023/day-15/two.go

package main

import (
	"strings"

	"github.com/elliotchance/orderedmap/v2"
)

var boxes = map[int]*orderedmap.OrderedMap[string, int]{}

// add places a lense into an ordered box
func add(id int, label string, focalLength int) {
	boxes[id].Set(label, focalLength)
}

// remove takes a lense out of an ordered box
func remove(id int, label string) {
	boxes[id].Delete(strings.TrimRight(label, "-"))
}

// two returns the sum of all lense configurations
func two(lines []string) int {
	hash := newHasher()

	for _, lense := range lenses {
		label, focalLength := func() (string, int) {
			x := strings.Split(lense, "=")
			if len(x) == 2 {
				return x[0], mustConv(x[1])
			}
			return strings.TrimRight(x[0], "-"), 0
		}()
		boxId := hash.run(label)

		_, ok := boxes[boxId]
		if !ok {
			m := orderedmap.NewOrderedMap[string, int]()
			boxes[boxId] = m
		}

		if strings.Contains(lense, "=") {
			add(boxId, label, focalLength)
		} else {
			remove(boxId, label)
		}
	}

	sum := 0
	for id, box := range boxes {
		for index, lense := range box.Keys() {
			focalLength, _ := box.Get(lense)
			sum += (id + 1) * (index + 1) * focalLength
		}
	}

	return sum
}