AoC Day 15, Parts 1 & 2 (Solved)

2023/15/code.go

@@ -0,0 +1,112 @@
+package main
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+
+	"github.com/jpillora/puzzler/harness/aoc"
+)
+
+func main() {
+	aoc.Harness(run)
+}
+
+// on code change, run will be executed 4 times:
+// 1. with: false (part1), and example input
+// 2. with: true (part2), and example input
+// 3. with: false (part1), and user input
+// 4. with: true (part2), and user input
+// the return value of each run is printed to stdout
+type Lense struct {
+	Label string
+	Focus int
+}
+
+func run(part2 bool, input string) any {
+	// when you're ready to do part 2, remove this "not implemented" block
+	if part2 {
+		boxes := make([][]Lense, 256)
+		for _, l := range strings.Split(input, "\n") {
+			if l == "" {
+				continue
+			}
+
+			for _, s := range strings.Split(l, ",") {
+				if strings.Contains(s, "-") {
+					// Dash logic
+					spl := strings.Split(s, "-")
+					label := spl[0]
+					box := hash(label)
+
+				remove:
+					for i := range boxes[box] {
+						if boxes[box][i].Label == label {
+							boxes[box] = append(boxes[box][:i], boxes[box][i+1:]...)
+							break remove
+						}
+					}
+
+				} else if strings.Contains(s, "=") {
+					// Eq logic
+					spl := strings.Split(s, "=")
+					label := spl[0]
+					lens, _ := strconv.Atoi(spl[1])
+
+					box := hash(label)
+
+					insert := Lense{label, lens}
+					replaced := false
+
+				replace:
+					for i := range boxes[box] {
+						if boxes[box][i].Label == label {
+							boxes[box][i] = insert
+							replaced = true
+							break replace
+						}
+					}
+
+					if !replaced {
+						boxes[box] = append(boxes[box], insert)
+					}
+
+				} else {
+					panic(fmt.Sprintf("bad control '%v'", s))
+				}
+			}
+		}
+
+		// Calculate
+		sum := 0
+		for b := range boxes {
+			for l := range boxes[b] {
+				val := (1 + b) * (1 + l) * boxes[b][l].Focus
+				sum += val
+			}
+		}
+
+		return sum
+	}
+	// solve part 1 here
+
+	hsum := 0
+	for _, l := range strings.Split(input, "\n") {
+		for _, s := range strings.Split(l, ",") {
+			hsum += hash(s)
+		}
+	}
+
+	return hsum
+}
+
+func hash(str string) int {
+	h := 0
+	for _, s := range str {
+		ascii := int(rune(s))
+		h += ascii
+		h *= 17
+		h = h % 256
+	}
+	return h
+}