adventofcode/2023/day15/main.go

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2023-12-15 13:20:13 +00:00
package main
import (
"fmt"
"strings"
h "git.bullercodeworks.com/brian/adventofcode/helpers"
)
func main() {
inp := h.StdinToString()
part1(inp)
fmt.Println()
part2(inp)
}
func part1(input string) {
var res int
pts := strings.Split(input, ",")
for i := range pts {
res += hash(pts[i])
}
fmt.Println("# Part 1")
fmt.Println(res)
}
func part2(input string) {
var boxes []*Box
for i := 1; i <= 256; i++ {
boxes = append(boxes, &Box{num: i})
}
for _, v := range strings.Split(input, ",") {
l := NewLens(v)
if l.focalLength == -1 {
// Remove
boxes[l.box].Remove(l)
} else {
// Add/Replace
boxes[l.box].Add(l)
}
}
var res int
for i := range boxes {
res += boxes[i].FocusingPower()
}
fmt.Println("# Part 2")
fmt.Println(res)
}
type Box struct {
num int
lenses []*Lens
}
func (b *Box) Add(l *Lens) {
for i := range b.lenses {
if b.lenses[i].label == l.label {
b.lenses[i] = l
return
}
}
b.lenses = append(b.lenses, l)
}
func (b *Box) Remove(l *Lens) {
for i := range b.lenses {
if b.lenses[i].label == l.label {
b.lenses = append(b.lenses[:i], b.lenses[i+1:]...)
return
}
}
}
func (b *Box) FocusingPower() int {
var res int
for i := range b.lenses {
var lensRes int
lensRes = b.num
lensRes *= i + 1
lensRes *= b.lenses[i].focalLength
res += lensRes
}
return res
}
type Lens struct {
label string
focalLength int
box int
}
func NewLens(inp string) *Lens {
if strings.Contains(inp, "=") {
pts := strings.Split(inp, "=")
return &Lens{
label: pts[0],
focalLength: h.Atoi(pts[1]),
box: hash(pts[0]),
}
} else {
lbl := strings.TrimSuffix(inp, "-")
return &Lens{
label: lbl,
focalLength: -1,
box: hash(lbl),
}
}
}
func hash(inp string) int {
var res int
for _, i := range inp {
res += int(i)
res *= 17
res = res % 256
}
return res
}
func focusingPower(lens string, boxNum int, boxes [][]string) int {
res := boxNum + 1
for i := 1; i <= len(boxes[boxNum]); i++ {
if boxes[boxNum][i-1] == lens {
res *= i
break
}
}
return res
}