Completed both parts of Day 15 puzzle

day15/day15.go

@@ -0,0 +1,171 @@
+package day15
+
+import "strconv"
+
+func hash(bytes []byte) int {
+	val := 0
+	for _, b := range bytes {
+		val += int(b)
+		val *= 17
+		val %= 256
+	}
+	return val
+}
+
+func SumHashes(line string) int {
+	result := 0
+	l := []byte(line)
+
+	step := []byte{}
+
+	for _, b := range l {
+
+		if b == '\n' {
+			break
+		}
+
+		if b == ',' {
+			hashValue := hash(step)
+			result += hashValue
+			step = []byte{}
+		} else {
+			step = append(step, b)
+		}
+	}
+
+	return result
+}
+
+type Lense struct {
+	label string
+	focal int
+}
+type Lenses []*Lense
+
+type LensePresences map[string]int
+
+type Box struct {
+	lenses         Lenses
+	lensePresences LensePresences
+}
+
+func parseStep(bytes []byte) (string, byte, int) {
+	label := []byte{}
+	focal := []byte{}
+	parseFocal := false
+
+	for _, b := range bytes {
+		if b == '-' {
+			return string(label), '-', -1
+		}
+
+		if b == '=' {
+			parseFocal = true
+			continue
+		}
+
+		if parseFocal {
+			focal = append(focal, b)
+		} else {
+			label = append(label, b)
+		}
+
+	}
+
+	focalValue, _ := strconv.Atoi(string(focal))
+
+	return string(label), '=', focalValue
+}
+
+func removeLense(box *Box, label string) {
+	idx, ok := box.lensePresences[label]
+	if ok {
+		delete(box.lensePresences, label)
+
+		/*
+			idx := 0
+			for i, lense := range box.lenses {
+				if lense.label == label {
+					idx = i
+					break
+				}
+			}
+		*/
+
+		for i := idx; i < len(box.lenses)-1; i++ {
+			box.lenses[i] = box.lenses[i+1]
+			box.lensePresences[box.lenses[i].label] = i
+		}
+
+		box.lenses = box.lenses[0 : len(box.lenses)-1]
+	}
+}
+
+func addOrChangeLense(box *Box, label string, focal int) {
+	newLense := &Lense{label, focal}
+
+	idx, ok := box.lensePresences[label]
+	if ok { // change lense
+		box.lenses[idx] = newLense
+	} else {
+		// add lense
+		box.lenses = append(box.lenses, newLense)
+		box.lensePresences[label] = len(box.lenses) - 1
+	}
+}
+
+func SumBoxes(line string) int {
+	l := []byte(line)
+	boxes := make([]*Box, 256)
+
+	step := []byte{}
+
+	for _, b := range l {
+
+		if b == '\n' {
+			break
+		}
+
+		if b == ',' {
+			label, operator, focal := parseStep(step)
+			labelHash := hash([]byte(label))
+
+			box := boxes[labelHash]
+			if box == nil {
+				box = &Box{Lenses{}, LensePresences{}}
+				boxes[labelHash] = box
+			}
+
+			if operator == '-' {
+				removeLense(box, label)
+				if len(box.lenses) == 0 {
+					box = nil
+					boxes[labelHash] = nil
+				}
+			} else {
+				addOrChangeLense(box, label, focal)
+			}
+
+			step = []byte{}
+		} else {
+			step = append(step, b)
+		}
+	}
+
+	sum := 0
+	for i, box := range boxes {
+		if box != nil {
+			boxNumber := i + 1
+
+			for j, lense := range box.lenses {
+				slotNumber := j + 1
+
+				focusingPower := boxNumber * slotNumber * lense.focal
+				sum += focusingPower
+			}
+
+		}
+	}
+
+	return sum
+}

day15/day15_test.go

@@ -0,0 +1,75 @@
+package day15
+
+import (
+	"testing"
+
+	"gitea.paas.celticinfo.fr/oabrivard/aoc2023/utils"
+)
+
+func TestHash(t *testing.T) {
+	result := hash([]byte("rn=1"))
+
+	if result != 30 {
+		t.Fatalf("expected 30, got %v", result)
+	}
+
+	result = hash([]byte("cm-"))
+
+	if result != 253 {
+		t.Fatalf("expected 253, got %v", result)
+	}
+
+	result = hash([]byte("qp=3"))
+
+	if result != 97 {
+		t.Fatalf("expected 97, got %v", result)
+	}
+
+	result = hash([]byte("cm=2"))
+
+	if result != 47 {
+		t.Fatalf("expected 47, got %v", result)
+	}
+
+	result = hash([]byte("qp-"))
+
+	if result != 14 {
+		t.Fatalf("expected 14, got %v", result)
+	}
+}
+
+func TestSumHashes(t *testing.T) {
+	result := SumHashes("rn=1,cm-,qp=3,cm=2,qp-,pc=4,ot=9,ab=5,pc-,pc=6,ot=7,")
+
+	if result != 1320 {
+		t.Fatalf("expected 1320, got %v", result)
+	}
+}
+
+func TestSumHashesWithInput(t *testing.T) {
+	lines := utils.ReadLines("input.txt")
+
+	result := SumHashes(lines[0])
+
+	if result != 511416 {
+		t.Fatalf("expected 511416, got %v", result)
+	}
+}
+
+func TestSumBoxes(t *testing.T) {
+	result := SumBoxes("rn=1,cm-,qp=3,cm=2,qp-,pc=4,ot=9,ab=5,pc-,pc=6,ot=7,")
+
+	if result != 145 {
+		t.Fatalf("expected 145, got %v", result)
+	}
+}
+
+func TestSumBoxesWithInput(t *testing.T) {
+	lines := utils.ReadLines("input.txt")
+
+	result := SumBoxes(lines[0])
+
+	if result != 290779 {
+		t.Fatalf("expected 290779, got %v", result)
+	}
+}