2023 Day 15 Complete!

2023/day15/main.go

@@ -0,0 +1,128 @@
+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
+}