finish 2023

2023/go/day15/day15.go

@@ -0,0 +1,80 @@
+package day15
+
+import (
+	"adventofcode2023/utils"
+	_ "fmt"
+	"strings"
+)
+
+type Lens struct {
+	label	string
+	fl		int
+}
+
+func Part1(input string) int {
+	ans := 0
+	seqs := strings.Split(input, ",")
+	for _,seq := range seqs {
+		ans += hash(seq)
+	}
+	
+	return ans
+}
+
+func Part2(input string) int {
+	Boxes := [256][]Lens{}
+	cmds := strings.Split(input, ",")
+	for _,cmd := range cmds {
+		if cmd[len(cmd)-1] == '-' {
+			label := cmd[:len(cmd)-1]
+			hash := hash(label)
+			nl := []Lens{}
+			for _, lens := range Boxes[hash] {
+				if lens.label != label {
+					nl = append(nl, lens)
+				}
+			}
+			Boxes[hash] = nl
+		} else {
+			tokens := strings.Split(cmd, "=")
+			label := tokens[0]
+			fl := utils.MustAtoi(tokens[1])
+			hash := hash(label)
+			nl := []Lens{}
+			if len(Boxes[hash]) == 0 {
+				Boxes[hash] = append(Boxes[hash], Lens{label:label, fl:fl})
+			} else {
+				found := false
+				for _, lens := range Boxes[hash] {
+					if lens.label == label {
+						nl = append(nl, Lens{label:label, fl:fl})
+						found = true
+					} else {
+						nl = append(nl, lens)
+					}
+				}
+				Boxes[hash] = nl
+				if ! found {
+					Boxes[hash] = append(Boxes[hash], Lens{label:label, fl:fl})
+				}
+			}
+		}
+	}
+	ans := 0
+	for i, box := range Boxes {
+		for j, lens := range box {
+			ans += (i+1) * (j +1) * lens.fl
+		}
+	} 
+		return ans
+}
+
+func hash(in string) int {
+	result := 0
+	for _, letter := range in {
+		result += int(letter) 
+		result = result * 17
+		result = result % 256
+	}
+	return result
+}