feat: day 09

day09/day09.go

@@ -0,0 +1,112 @@
+package main
+
+import (
+	"github.com/julijane/advent-of-code-2024/aoc"
+)
+
+func calcPart1(line string) int {
+	fileblocks := []int{}
+	gaps := []int{}
+
+	for fileid, pos, i := 0, 0, 0; i < len(line); i, fileid = i+2, fileid+1 {
+		lengthFile := int(line[i] - '0')
+
+		for j := 0; j < lengthFile; j++ {
+			fileblocks = append(fileblocks, fileid)
+		}
+		pos += lengthFile
+
+		if i < len(line)-1 {
+			lengthGap := int(line[i+1] - '0')
+			if lengthGap >= 0 {
+				for j := 0; j < lengthGap; j, pos = j+1, pos+1 {
+					gaps = append(gaps, pos)
+				}
+			}
+		}
+	}
+
+	for _, gapPos := range gaps {
+		if gapPos > len(fileblocks) {
+			break
+		}
+		fileId := fileblocks[len(fileblocks)-1]
+		for pos := len(fileblocks) - 1; pos > gapPos; pos-- {
+			fileblocks[pos] = fileblocks[pos-1]
+		}
+		fileblocks[gapPos] = fileId
+	}
+
+	sum := 0
+	for pos, fileid := range fileblocks {
+		sum += pos * fileid
+	}
+
+	return sum
+}
+
+type File struct {
+	ID     int
+	Pos    int
+	Length int
+}
+
+func calcPart2(line string) int {
+	files := []File{}
+	gaps := []File{}
+
+	for fileid, pos, i := 0, 0, 0; i < len(line); i, fileid = i+2, fileid+1 {
+		lengthFile := int(line[i] - '0')
+		files = append(files, File{ID: fileid, Pos: pos, Length: lengthFile})
+		pos += lengthFile
+
+		if i < len(line)-1 {
+			lengthGap := int(line[i+1] - '0')
+			gaps = append(gaps, File{ID: -1, Pos: pos, Length: lengthGap})
+			pos += lengthGap
+		}
+	}
+
+	for i := len(files) - 1; i >= 0; i-- {
+		if len(gaps) == 0 {
+			break
+		}
+
+		for j, gap := range gaps {
+			if gap.Pos > files[i].Pos {
+				break
+			}
+
+			if gap.Length >= files[i].Length {
+				files[i].Pos = gap.Pos
+				if gap.Length > files[i].Length {
+					gaps[j].Pos += files[i].Length
+					gaps[j].Length -= files[i].Length
+				} else {
+					gaps = append(gaps[:j], gaps[j+1:]...)
+				}
+				break
+			}
+		}
+	}
+
+	sum := 0
+	for _, file := range files {
+		for pos := file.Pos; pos < file.Pos+file.Length; pos++ {
+			sum += pos * file.ID
+		}
+	}
+
+	return sum
+}
+
+func calc(input *aoc.Input, doPart1, doPart2 bool) (int, int) {
+	line := input.PlainLines()[0]
+
+	return calcPart1(line), calcPart2(line)
+}
+
+func main() {
+	aoc.Run("sample1.txt", calc, true, true)
+	aoc.Run("input.txt", calc, true, true)
+}