diff --git a/.gitignore b/.gitignore
index 3943db3..0349634 100644
--- a/.gitignore
+++ b/.gitignore
@@ -26,7 +26,7 @@ go.work.sum
 .env
 
 # input files
-**/testdata/*.txt
+**/testdata/*
 
 # scaffold
 mkfiles.sh
\ No newline at end of file
diff --git a/day-09/benchmark b/day-09/benchmark
new file mode 100644
index 0000000..26e8a07
--- /dev/null
+++ b/day-09/benchmark
@@ -0,0 +1,15 @@
+goos: linux
+goarch: amd64
+pkg: github.com/onyx-and-iris/aoc2024/day-09
+cpu: Intel(R) Core(TM) i7-8700K CPU @ 3.70GHz
+BenchmarkSolve-12    	       1	22886096949 ns/op
+BenchmarkSolve-12    	       1	22884217914 ns/op
+BenchmarkSolve-12    	       1	22924853520 ns/op
+BenchmarkSolve-12    	       1	23014082753 ns/op
+BenchmarkSolve-12    	       1	22788595898 ns/op
+BenchmarkSolve-12    	       1	22781925171 ns/op
+BenchmarkSolve-12    	       1	23094890275 ns/op
+BenchmarkSolve-12    	       1	22694434858 ns/op
+BenchmarkSolve-12    	       1	23002190907 ns/op
+BenchmarkSolve-12    	       1	22923138789 ns/op
+ok  	github.com/onyx-and-iris/aoc2024/day-09	229.003s
diff --git a/day-09/cmd/cli/main.go b/day-09/cmd/cli/main.go
new file mode 100644
index 0000000..7b87447
--- /dev/null
+++ b/day-09/cmd/cli/main.go
@@ -0,0 +1,41 @@
+/********************************************************************************
+    Advent of Code 2024 - day-09
+********************************************************************************/
+
+package main
+
+import (
+	"embed"
+	"flag"
+	"fmt"
+	"slices"
+
+	log "github.com/sirupsen/logrus"
+
+	problems "github.com/onyx-and-iris/aoc2024/day-09"
+)
+
+//go:embed testdata
+var files embed.FS
+
+func main() {
+	filename := flag.String("f", "input.txt", "input file")
+	loglevel := flag.Int("l", int(log.InfoLevel), "log level")
+	flag.Parse()
+
+	if slices.Contains(log.AllLevels, log.Level(*loglevel)) {
+		log.SetLevel(log.Level(*loglevel))
+	}
+
+	data, err := files.ReadFile(fmt.Sprintf("testdata/%s", *filename))
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	one, two, err := problems.Solve(data)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Printf("solution one: %d\nsolution two: %d\n", one, two)
+}
diff --git a/day-09/go.mod b/day-09/go.mod
new file mode 100644
index 0000000..01f0c53
--- /dev/null
+++ b/day-09/go.mod
@@ -0,0 +1,7 @@
+module github.com/onyx-and-iris/aoc2024/day-09
+
+go 1.23.3
+
+require github.com/sirupsen/logrus v1.9.3
+
+require golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8 // indirect
diff --git a/day-09/go.sum b/day-09/go.sum
new file mode 100644
index 0000000..21f9bfb
--- /dev/null
+++ b/day-09/go.sum
@@ -0,0 +1,15 @@
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/sirupsen/logrus v1.9.3 h1:dueUQJ1C2q9oE3F7wvmSGAaVtTmUizReu6fjN8uqzbQ=
+github.com/sirupsen/logrus v1.9.3/go.mod h1:naHLuLoDiP4jHNo9R0sCBMtWGeIprob74mVsIT4qYEQ=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
+github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8 h1:0A+M6Uqn+Eje4kHMK80dtF3JCXC4ykBgQG4Fe06QRhQ=
+golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/day-09/internal/one/benchmark b/day-09/internal/one/benchmark
new file mode 100644
index 0000000..53dd601
--- /dev/null
+++ b/day-09/internal/one/benchmark
@@ -0,0 +1,6 @@
+goos: linux
+goarch: amd64
+pkg: github.com/onyx-and-iris/aoc2024/day-09/internal/one
+cpu: Intel(R) Core(TM) i7-8700K CPU @ 3.70GHz
+BenchmarkSolve-12    	1000000000	         0.1535 ns/op
+ok  	github.com/onyx-and-iris/aoc2024/day-09/internal/one	1.893s
diff --git a/day-09/internal/one/block.go b/day-09/internal/one/block.go
new file mode 100644
index 0000000..ed2ad8e
--- /dev/null
+++ b/day-09/internal/one/block.go
@@ -0,0 +1,8 @@
+package one
+
+const empty = -1
+
+type block struct {
+	used int
+	free int
+}
diff --git a/day-09/internal/one/disk.go b/day-09/internal/one/disk.go
new file mode 100644
index 0000000..2c9fa62
--- /dev/null
+++ b/day-09/internal/one/disk.go
@@ -0,0 +1,59 @@
+package one
+
+import (
+	"fmt"
+	"slices"
+	"strings"
+)
+
+type disk struct {
+	data      []int
+	totalUsed int
+}
+
+func newDisk(blocks []block) disk {
+	var totalUsed int
+	data := []int{}
+	for id, block := range blocks {
+		for range block.used {
+			data = append(data, id)
+		}
+		for range block.free {
+			data = append(data, empty)
+		}
+		totalUsed += block.used
+	}
+
+	return disk{
+		data:      data,
+		totalUsed: totalUsed,
+	}
+}
+
+func (d *disk) len() int {
+	return d.totalUsed
+}
+
+func (d *disk) sort() {
+	for i := len(d.data) - 1; i >= 0; i-- {
+		if d.data[i] != empty {
+			indx := slices.Index(d.data, empty)
+			if indx == d.len() {
+				break
+			}
+			d.data[i], d.data[indx] = d.data[indx], d.data[i]
+		}
+	}
+}
+
+func (d *disk) debug() string {
+	var sb strings.Builder
+	for _, n := range d.data {
+		if n == empty {
+			sb.WriteRune('.')
+		} else {
+			sb.WriteString(fmt.Sprintf("%d", n))
+		}
+	}
+	return sb.String()
+}
diff --git a/day-09/internal/one/solve.go b/day-09/internal/one/solve.go
new file mode 100644
index 0000000..318aa1d
--- /dev/null
+++ b/day-09/internal/one/solve.go
@@ -0,0 +1,27 @@
+package one
+
+import (
+	"bytes"
+
+	log "github.com/sirupsen/logrus"
+)
+
+func Solve(buf []byte) (int, error) {
+	r := bytes.NewReader(buf)
+	blocks, err := parseLines(r)
+	if err != nil {
+		return 0, err
+	}
+
+	disk := newDisk(blocks)
+	disk.sort()
+	log.Debug(disk.debug())
+
+	var i, checksum int
+	for range disk.len() {
+		checksum += i * disk.data[i]
+		i++
+	}
+
+	return checksum, nil
+}
diff --git a/day-09/internal/one/solve_internal_test.go b/day-09/internal/one/solve_internal_test.go
new file mode 100644
index 0000000..e5fd7ea
--- /dev/null
+++ b/day-09/internal/one/solve_internal_test.go
@@ -0,0 +1,15 @@
+package one
+
+import (
+	_ "embed"
+	"os"
+	"testing"
+)
+
+//go:embed testdata/input.txt
+var data []byte
+
+func BenchmarkSolve(b *testing.B) {
+	os.Stdout, _ = os.Open(os.DevNull)
+	Solve(data)
+}
diff --git a/day-09/internal/one/util.go b/day-09/internal/one/util.go
new file mode 100644
index 0000000..cac3426
--- /dev/null
+++ b/day-09/internal/one/util.go
@@ -0,0 +1,38 @@
+package one
+
+import (
+	"bufio"
+	"io"
+	"strconv"
+)
+
+func parseLines(r io.Reader) ([]block, error) {
+	var blocks []block
+
+	scanner := bufio.NewScanner(r)
+	for scanner.Scan() {
+		line := scanner.Text()
+
+		for i := 0; i < len(line); i += 2 {
+			var free int
+			if i < len(line)-1 {
+				free = mustConv(string(line[i+1]))
+			}
+			blocks = append(blocks, block{mustConv(string(line[i])), free})
+		}
+	}
+
+	if err := scanner.Err(); err != nil {
+		return []block{}, err
+	}
+
+	return blocks, nil
+}
+
+func mustConv(s string) int {
+	n, err := strconv.Atoi(s)
+	if err != nil {
+		panic(err)
+	}
+	return n
+}
diff --git a/day-09/internal/two/benchmark b/day-09/internal/two/benchmark
new file mode 100644
index 0000000..63d5825
--- /dev/null
+++ b/day-09/internal/two/benchmark
@@ -0,0 +1,6 @@
+goos: linux
+goarch: amd64
+pkg: github.com/onyx-and-iris/aoc2024/day-09/internal/two
+cpu: Intel(R) Core(TM) i7-8700K CPU @ 3.70GHz
+BenchmarkSolve-12    	       1	22722704246 ns/op
+ok  	github.com/onyx-and-iris/aoc2024/day-09/internal/two	22.726s
diff --git a/day-09/internal/two/block.go b/day-09/internal/two/block.go
new file mode 100644
index 0000000..bdba996
--- /dev/null
+++ b/day-09/internal/two/block.go
@@ -0,0 +1,21 @@
+package two
+
+const empty = -1
+
+type block struct {
+	used   int
+	free   []int
+	offset int
+}
+
+func newBlock(used, start, end int) block {
+	return block{
+		used:   used,
+		free:   []int{start, start + end},
+		offset: 0,
+	}
+}
+
+func (b *block) available() int {
+	return b.free[1] - b.free[0]
+}
diff --git a/day-09/internal/two/disk.go b/day-09/internal/two/disk.go
new file mode 100644
index 0000000..302177a
--- /dev/null
+++ b/day-09/internal/two/disk.go
@@ -0,0 +1,98 @@
+package two
+
+import (
+	"fmt"
+	"strings"
+
+	log "github.com/sirupsen/logrus"
+)
+
+type disk struct {
+	blocks []block
+	data   []int
+}
+
+func newDisk(blocks []block) disk {
+	offset := 0
+	data := []int{}
+	for id, block := range blocks {
+		blocks[id].offset = offset
+		for range block.used {
+			data = append(data, id)
+		}
+		for range block.available() {
+			data = append(data, empty)
+		}
+		offset += block.used + block.available()
+	}
+
+	return disk{
+		blocks: blocks,
+		data:   data,
+	}
+}
+
+func (d *disk) sort() {
+	for i := len(d.blocks) - 1; i >= 0; i-- {
+		log.Debugf("searching for space for block %d of size %d\n", i, d.blocks[i].used)
+
+		for j := 0; j < len(d.data); j++ {
+			if j >= d.blocks[i].offset+d.blocks[i].used {
+				break
+			}
+
+			if d.data[j] != empty {
+				continue
+			}
+
+			var sz int
+			if d.data[j] == empty {
+				sz = d.sizeOfEmptyBlock(j)
+			}
+
+			if d.blocks[i].used <= sz {
+				d.writeBlockToDisk(j, d.blocks[i])
+				// don't attempt to write block again
+				break
+			}
+
+			// skip to end of empty block
+			j += sz
+		}
+	}
+}
+
+func (d *disk) sizeOfEmptyBlock(j int) int {
+	var sz int
+	for k := j; k < len(d.data) && d.data[k] == empty; k++ {
+		sz++
+	}
+	log.Debugf("found empty space of size %d\n", sz)
+	return sz
+}
+
+func (d *disk) writeBlockToDisk(start int, b block) {
+	for i := b.offset; i < b.offset+b.used; i, start = i+1, start+1 {
+		d.data[start] = d.data[i]
+		log.Debugf("writing %d to disk at pos %d\n", d.data[i], start)
+	}
+
+	for i := b.offset; i < len(d.data) && i < b.offset+b.used; i++ {
+		d.data[i] = empty
+		log.Debugf("truncating space on disk at pos %d", i)
+	}
+
+	log.Debug(d.debug())
+}
+
+func (d *disk) debug() string {
+	var sb strings.Builder
+	for _, n := range d.data {
+		if n == empty {
+			sb.WriteRune('.')
+		} else {
+			sb.WriteString(fmt.Sprintf("%d", n))
+		}
+	}
+	return sb.String()
+}
diff --git a/day-09/internal/two/solve.go b/day-09/internal/two/solve.go
new file mode 100644
index 0000000..fa1e90f
--- /dev/null
+++ b/day-09/internal/two/solve.go
@@ -0,0 +1,31 @@
+package two
+
+import (
+	"bytes"
+
+	log "github.com/sirupsen/logrus"
+)
+
+func Solve(buf []byte) (int, error) {
+	r := bytes.NewReader(buf)
+	blocks, err := parseLines(r)
+	if err != nil {
+		return 0, err
+	}
+
+	disk := newDisk(blocks)
+	log.Debug(disk.debug())
+	disk.sort()
+	log.Debug(disk.debug())
+
+	var checksum int
+	for i := 0; i < len(disk.data); i++ {
+		if disk.data[i] == empty {
+			continue
+		}
+
+		checksum += i * disk.data[i]
+	}
+
+	return checksum, nil
+}
diff --git a/day-09/internal/two/solve_internal_test.go b/day-09/internal/two/solve_internal_test.go
new file mode 100644
index 0000000..ecb05d5
--- /dev/null
+++ b/day-09/internal/two/solve_internal_test.go
@@ -0,0 +1,15 @@
+package two
+
+import (
+	_ "embed"
+	"os"
+	"testing"
+)
+
+//go:embed testdata/input.txt
+var data []byte
+
+func BenchmarkSolve(b *testing.B) {
+	os.Stdout, _ = os.Open(os.DevNull)
+	Solve(data)
+}
diff --git a/day-09/internal/two/util.go b/day-09/internal/two/util.go
new file mode 100644
index 0000000..59911f5
--- /dev/null
+++ b/day-09/internal/two/util.go
@@ -0,0 +1,41 @@
+package two
+
+import (
+	"bufio"
+	"io"
+	"strconv"
+)
+
+func parseLines(r io.Reader) ([]block, error) {
+	var blocks []block
+	var start int
+
+	scanner := bufio.NewScanner(r)
+	for scanner.Scan() {
+		line := scanner.Text()
+
+		for i := 0; i < len(line); i += 2 {
+			used := mustConv(string(line[i]))
+			start += used
+			var end int
+			if i < len(line)-1 {
+				end = mustConv(string(line[i+1]))
+			}
+			blocks = append(blocks, newBlock(used, start, end))
+		}
+	}
+
+	if err := scanner.Err(); err != nil {
+		return []block{}, err
+	}
+
+	return blocks, nil
+}
+
+func mustConv(s string) int {
+	n, err := strconv.Atoi(s)
+	if err != nil {
+		panic(err)
+	}
+	return n
+}
diff --git a/day-09/makefile b/day-09/makefile
new file mode 100644
index 0000000..43e40bb
--- /dev/null
+++ b/day-09/makefile
@@ -0,0 +1,30 @@
+program = day-09
+
+GO = go
+SRC_DIR := src
+BIN_DIR := bin
+
+EXE := $(BIN_DIR)/$(program)
+
+.DEFAULT_GOAL := build
+
+.PHONY: fmt vet build bench clean
+fmt:        
+	$(GO) fmt ./...
+
+vet: fmt        
+	$(GO) vet ./...
+
+build: vet | $(BIN_DIR)
+	$(GO) build -o $(EXE) ./$(SRC_DIR)
+
+bench:
+	$(GO) test ./internal/one/ -bench=. > internal/one/benchmark
+	$(GO) test ./internal/two/ -bench=. > internal/two/benchmark
+	$(GO) test . -count=10 -bench=. > benchmark
+
+$(BIN_DIR):
+	@mkdir -p $@
+
+clean:
+	@rm -rv $(BIN_DIR)
diff --git a/day-09/solve.go b/day-09/solve.go
new file mode 100644
index 0000000..58f9a0b
--- /dev/null
+++ b/day-09/solve.go
@@ -0,0 +1,20 @@
+package daynine
+
+import (
+	"github.com/onyx-and-iris/aoc2024/day-09/internal/one"
+	"github.com/onyx-and-iris/aoc2024/day-09/internal/two"
+)
+
+func Solve(buf []byte) (int, int, error) {
+	answerOne, err := one.Solve(buf)
+	if err != nil {
+		return 0, 0, err
+	}
+
+	answerTwo, err := two.Solve(buf)
+	if err != nil {
+		return 0, 0, err
+	}
+
+	return answerOne, answerTwo, nil
+}
diff --git a/day-09/solve_internal_test.go b/day-09/solve_internal_test.go
new file mode 100644
index 0000000..bfd668b
--- /dev/null
+++ b/day-09/solve_internal_test.go
@@ -0,0 +1,15 @@
+package daynine
+
+import (
+	_ "embed"
+	"os"
+	"testing"
+)
+
+//go:embed testdata/input.txt
+var data []byte
+
+func BenchmarkSolve(b *testing.B) {
+	os.Stdout, _ = os.Open(os.DevNull)
+	Solve(data)
+}