commit a67735e3611d42e2b0b03339bfef759da3c4f148
Author: Gabriel Bizdoc <gabriel.bizdoc@gmail.com>
Date:   Thu Dec 4 00:41:23 2025 +0200

    init

diff --git a/aocutils/utils.go b/aocutils/utils.go
new file mode 100644
index 0000000..50d5b84
--- /dev/null
+++ b/aocutils/utils.go
@@ -0,0 +1,27 @@
+package aocutils
+
+import (
+	"bytes"
+	"io"
+)
+
+func SplitComma(data []byte, atEOF bool) (advance int, token []byte, err error) {
+	if atEOF && len(data) == 0 {
+		return 0, nil, nil
+	}
+	if i := bytes.IndexByte(data, ','); i >= 0 {
+		return i + 1, data[0:i], nil
+	}
+	if atEOF {
+		return len(data), data, nil
+	}
+	return 0, nil, nil
+}
+
+func ReadString(r io.Reader) (string, error) {
+	buff, err := io.ReadAll(r)
+	if err != nil {
+		return "", err
+	}
+	return string(buff), nil
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..68ea8ff
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module git.bizdoc.ro/public/Advent-of-Code.git
+
+go 1.25.1
diff --git a/year25/day1.go b/year25/day1.go
new file mode 100644
index 0000000..c800362
--- /dev/null
+++ b/year25/day1.go
@@ -0,0 +1,150 @@
+package year25
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"iter"
+	"log"
+	"strconv"
+)
+
+func Day1Part1(r io.Reader, l *log.Logger) (any, error) {
+	dial := 50
+	solution := 0
+	for pair := range day1GetPairs(r) {
+		dial += pair.MustValue()
+		dial %= 100
+		if dial < 0 {
+			dial = 100 + dial
+		}
+		if dial == 0 {
+			solution += 1
+		}
+		l.Printf("The dial is rotated %s(%d) to point at 0 `once` \n", pair, pair.MustValue())
+	}
+
+	return solution, nil
+}
+
+func Day1Part2Slow(r io.Reader, l *log.Logger) (any, error) {
+	dial := 50
+	solution := 0
+	for pair := range day1GetPairs(r) {
+		nextDial, count := day1AdvanceSimulation(dial, pair.MustValue())
+		dial = nextDial
+		solution += count
+
+		if count > 0 {
+			l.Printf("The dial is rotated %s(%d) to point at %d, during this points to 0 (%d)\n", pair, pair.MustValue(), dial, count)
+		} else {
+			l.Printf("The dial is rotated %s(%d) to point at %d\n", pair, pair.MustValue(), dial)
+		}
+	}
+
+	return solution, nil
+}
+
+func Day1Part2Fast(r io.Reader, l *log.Logger) (any, error) {
+	dial := 50
+	solution := 0
+	for pair := range day1GetPairs(r) {
+		value := pair.MustValue()
+
+		nextDial, count := day1Advance(dial, value)
+
+		dial = nextDial
+		solution += count
+
+		if count > 0 {
+			l.Printf("The dial is rotated %s(%d) to point at %d, during this points to 0 (%d)\n", pair, pair.MustValue(), dial, count)
+		} else {
+			l.Printf("The dial is rotated %s(%d) to point at %d\n", pair, pair.MustValue(), dial)
+		}
+	}
+
+	return solution, nil
+}
+
+func day1GetPairs(r io.Reader) iter.Seq[Day1Pair] {
+	return func(yield func(Day1Pair) bool) {
+		scanner := bufio.NewScanner(r)
+		scanner.Split(bufio.ScanLines)
+		for scanner.Scan() {
+			pair := Day1Pair(scanner.Text())
+			if !yield(pair) {
+				return
+			}
+		}
+		if err := scanner.Err(); err != nil {
+			panic(err)
+		}
+	}
+}
+
+type Day1Pair string
+
+func (p Day1Pair) Value() (int, error) {
+	valueStr := string(p[1:])
+	v, err := strconv.Atoi(valueStr)
+	if err != nil {
+		return 0, fmt.Errorf("failed to convert action value to int")
+	}
+	switch p[0] {
+	case 'L':
+		return -v, nil
+	case 'R':
+		return v, nil
+	default:
+		return 0, fmt.Errorf("unknown action value %q", p[0])
+	}
+}
+func (p Day1Pair) MustValue() int {
+	v, err := p.Value()
+	if err != nil {
+		panic(err)
+	}
+	return v
+}
+
+func day1AdvanceSimulation(dial int, value int) (int, int) {
+	solution := 0
+	for value < 0 {
+		value += 1
+		dial -= 1
+		if dial == 0 {
+			solution += 1
+		}
+		if dial == -1 {
+			dial = 99
+		}
+	}
+	for value > 0 {
+		value -= 1
+		dial += 1
+		if dial == 100 {
+			dial = 0
+			solution += 1
+		}
+	}
+
+	return dial, solution
+}
+
+func day1Advance(dial, step int) (next int, count int) {
+	next = dial + step
+	count += next / 100
+	if count < 0 {
+		count = -count
+	}
+
+	next = next % 100
+	if dial != 0 && step < 0 && next <= 0 {
+		count += 1
+	}
+
+	if next < 0 {
+		next += 100
+	}
+	return
+}
diff --git a/year25/day1_test.go b/year25/day1_test.go
new file mode 100644
index 0000000..483158a
--- /dev/null
+++ b/year25/day1_test.go
@@ -0,0 +1,161 @@
+package year25
+
+import (
+	"testing"
+)
+
+func TestMod(t *testing.T) {
+	a := -100
+	b := 100
+	t.Log(a % b)
+}
+
+func TestDial(t *testing.T) {
+	type Args struct {
+		From int
+		Step int
+
+		NextDial int
+		Count    int
+	}
+	type TestCase struct {
+		Name string
+		Args
+	}
+	args := func(from, step int) Args {
+		a := Args{
+			From: from,
+			Step: step,
+		}
+		a.NextDial, a.Count = simulateDial(from, step)
+		return a
+	}
+	cases := []TestCase{
+		{
+			Name: "from 50 add 10",
+			Args: args(50, 10),
+		},
+		{
+			Name: "from 50 add -10",
+			Args: args(50, -10),
+		},
+		{
+			Name: "from 50 add 50",
+			Args: args(50, 50),
+		},
+		{
+			Name: "from 50 add 70",
+			Args: args(50, 70),
+		},
+		{
+			Name: "from 50 add 150",
+			Args: args(50, 150),
+		},
+		{
+			Name: "from 50 add 155",
+			Args: args(50, 155),
+		},
+		{
+			Name: "from 50 add 10_000",
+			Args: args(50, 10_000),
+		},
+		{
+			Name: "from 50 add -1",
+			Args: args(50, -1),
+		},
+		{
+			Name: "from 50 add -10",
+			Args: args(50, -10),
+		},
+		{
+			Name: "from 50 add -50",
+			Args: args(50, -50),
+		},
+		{
+			Name: "from 50 add -70",
+			Args: args(50, -70),
+		},
+		{
+			Name: "from 50 add -100",
+			Args: args(50, -100),
+		},
+		{
+			Name: "from 50 add -150",
+			Args: args(50, -150),
+		},
+		{
+			Name: "from 50 add -10_000",
+			Args: args(50, -10_000),
+		},
+		{
+			Name: "from 50 add 10_000",
+			Args: args(50, 10_000),
+		},
+		{
+			Name: "from 0 add 50",
+			Args: args(0, 50),
+		},
+		{
+			Name: "from 0 add -50",
+			Args: args(0, -50),
+		},
+		{
+			Name: "from 0 add 100",
+			Args: args(0, 100),
+		},
+		{
+			Name: "from 0 add -100",
+			Args: args(0, -100),
+		},
+		{
+			Name: "from 0 add 10_000",
+			Args: args(0, 10_000),
+		},
+		{
+			Name: "from 0 add -10_000",
+			Args: args(0, -10_000),
+		},
+		{
+			Name: "from 22 add -34",
+			Args: args(22, -34),
+		},
+	}
+	for _, tc := range cases {
+		t.Run(tc.Name, func(t *testing.T) {
+			next, count := day1Advance(tc.From, tc.Step)
+			if next != tc.NextDial {
+				t.Errorf("next do not match got %d, want %d", next, tc.NextDial)
+			}
+			if count != tc.Count {
+				t.Errorf("count do not match got %d, want %d", count, tc.Count)
+			}
+			if !t.Failed() {
+				t.Log(tc.Name, "ok", "want:", count, "got:", count)
+			}
+		})
+	}
+}
+
+func simulateDial(dial int, value int) (int, int) {
+	solution := int(0)
+	for value < 0 {
+		value += 1
+		dial -= 1
+		if dial == 0 {
+			solution += 1
+		}
+		if dial == -1 {
+			dial = 99
+		}
+	}
+	for value > 0 {
+		value -= 1
+		dial += 1
+		if dial == 100 {
+			dial = 0
+			solution += 1
+		}
+	}
+
+	return dial, solution
+}
diff --git a/year25/day2.go b/year25/day2.go
new file mode 100644
index 0000000..7f5ef14
--- /dev/null
+++ b/year25/day2.go
@@ -0,0 +1,223 @@
+package year25
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	"log"
+	"strconv"
+	"strings"
+
+	"git.bizdoc.ro/private/Advent-of-Code.git/pkg/aocutils"
+)
+
+type day2Scanner struct {
+	scanner *bufio.Scanner
+	sep     byte
+	a, b    int
+	err     error
+}
+
+func (s *day2Scanner) Err() error {
+	return s.err
+}
+func (s *day2Scanner) Scan() bool {
+	if s.scanner.Scan() {
+		interval := s.scanner.Bytes()
+		i := bytes.IndexByte(interval, s.sep)
+		if i <= 0 {
+			s.err = fmt.Errorf("interval separator not found in line %s", string(interval))
+			return false
+		}
+		start := interval[:i]
+		end := interval[i+1:]
+
+		s.a, s.err = strconv.Atoi(string(start))
+		if s.err != nil {
+			s.err = fmt.Errorf("failed to scann number: %s", s.err)
+			return false
+		}
+		s.b, s.err = strconv.Atoi(string(end))
+		if s.err != nil {
+			s.err = fmt.Errorf("failed to scann number: %s", s.err)
+			return false
+		}
+		return true
+	}
+	return false
+}
+func (s *day2Scanner) Bounds() (int, int) {
+	return s.a, s.b
+}
+
+func Day2Part1Simple(r io.Reader, l *log.Logger) (any, error) {
+	input, err := aocutils.ReadString(r)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read input: %s", err)
+	}
+	ranges := strings.Split(strings.TrimSpace(input), ",")
+
+	isRepeated := func(n int) bool {
+		str := strconv.Itoa(n)
+		if len(str)%2 != 0 {
+			return false
+		}
+		half := len(str) / 2
+		return str[:half] == str[half:]
+	}
+
+	var sum int
+
+	for _, r := range ranges {
+		parts := strings.Split(r, "-")
+		if len(parts) != 2 {
+			continue
+		}
+
+		start, err := strconv.Atoi(parts[0])
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse number: %s", parts[0])
+		}
+
+		end, err := strconv.Atoi(parts[1])
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse number: %s", parts[1])
+		}
+
+		for v := start; v <= end; v++ {
+			if isRepeated(v) {
+				sum += v
+			}
+		}
+	}
+
+	return sum, nil
+}
+
+func Day2Part2Simple(r io.Reader, l *log.Logger) (any, error) {
+	input, err := aocutils.ReadString(r)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read input: %s", err)
+	}
+	ranges := strings.Split(strings.TrimSpace(input), ",")
+
+	isRepeated := func(n int) bool {
+		s := strconv.Itoa(n)
+		l := len(s)
+
+		// Try all possible pattern lengths
+		for p := 1; p*2 <= l; p++ { // p <= l/2 ensures at least 2 repeats
+			if l%p != 0 {
+				continue
+			}
+
+			pat := s[:p]
+			ok := true
+			for i := 0; i < l; i += p {
+				if s[i:i+p] != pat {
+					ok = false
+					break
+				}
+			}
+			if ok {
+				return true
+			}
+		}
+		return false
+	}
+
+	var sum int
+
+	for _, r := range ranges {
+		parts := strings.Split(r, "-")
+		if len(parts) != 2 {
+			continue
+		}
+
+		start, err := strconv.Atoi(parts[0])
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse number: %s", parts[0])
+		}
+
+		end, err := strconv.Atoi(parts[1])
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse number: %s", parts[1])
+		}
+
+		for v := start; v <= end; v++ {
+			if isRepeated(v) {
+				sum += v
+			}
+		}
+	}
+
+	return sum, nil
+}
+
+func Day2Part1(r io.Reader, logger *log.Logger) (any, error) {
+	inputScanner := bufio.NewScanner(r)
+	inputScanner.Split(aocutils.SplitComma)
+	scanner := &day2Scanner{scanner: inputScanner, sep: '-'}
+
+	var sum int
+
+	for scanner.Scan() {
+		start, end := scanner.Bounds()
+		logger.Println(start, "-", end)
+
+		for i := start; i <= end; i++ {
+			str := []byte(strconv.Itoa(i))
+			if len(str)%2 == 0 {
+				firstHalf := str[:len(str)/2]
+				secondHalf := str[len(str)/2:]
+				if bytes.Equal(firstHalf, secondHalf) {
+					logger.Println("found ", i)
+					sum += i
+				}
+			}
+		}
+	}
+
+	return sum, scanner.Err()
+}
+
+func Day2Part2(r io.Reader, logger *log.Logger) (any, error) {
+	inputScanner := bufio.NewScanner(r)
+	inputScanner.Split(aocutils.SplitComma)
+
+	scanner := &day2Scanner{scanner: inputScanner, sep: '-'}
+
+	var sum int
+	for scanner.Scan() {
+		start, end := scanner.Bounds()
+		logger.Println(start, "-", end)
+
+		for i := start; i <= end; i++ {
+			str := []byte(strconv.Itoa(i))
+			for digitIndex := 1; digitIndex*2 <= len(str); digitIndex++ {
+				if len(str)%digitIndex != 0 {
+					// skip cant compare
+					continue
+				}
+
+				isInvalid := true
+
+				for chunkStart := digitIndex; chunkStart+digitIndex <= len(str); chunkStart += digitIndex {
+					if !bytes.Equal(str[0:digitIndex], str[chunkStart:chunkStart+digitIndex]) {
+						isInvalid = false
+						break
+					}
+				}
+
+				if isInvalid {
+					logger.Println("found ", i)
+					sum += i
+					break
+				}
+			}
+		}
+	}
+
+	return sum, scanner.Err()
+}
diff --git a/year25/day3.go b/year25/day3.go
new file mode 100644
index 0000000..07d8519
--- /dev/null
+++ b/year25/day3.go
@@ -0,0 +1,65 @@
+package year25
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"log"
+	"strings"
+)
+
+func Day3Part1(r io.Reader, l *log.Logger) (any, error) {
+	return Day3(r, l, 2)
+}
+func Day3Part2(r io.Reader, l *log.Logger) (any, error) {
+	return Day3(r, l, 12)
+}
+func Day3(r io.Reader, logger *log.Logger, size int) (int64, error) {
+	scanner := bufio.NewScanner(r)
+	scanner.Split(bufio.ScanLines)
+	var sum int64
+
+	findLargetDigit := func(digits []rune) (rune, int) {
+		largestDigit := rune(0)
+		index := 0
+
+		for i := len(digits) - 1; i >= 0; i-- {
+			if digits[i] >= largestDigit {
+				largestDigit = digits[i]
+				index = i
+			}
+		}
+		return rune(largestDigit) - '0', index
+	}
+
+	for scanner.Scan() {
+		text := strings.TrimSpace(scanner.Text())
+		if text == "" {
+			continue
+		}
+		line := []rune(text)
+		parts := make([]byte, size)
+
+		for index := range parts {
+			digit, start := findLargetDigit(line[:len(line)+index-len(parts)+1])
+			line = line[start+1:]
+			if digit < 0 || digit > 9 {
+				return 0, fmt.Errorf("ivalid char '%c' in line %s", digit, text)
+			} else {
+				parts[index] = byte(digit)
+			}
+		}
+		logger.Println("line: ", text)
+
+		var partSum int64
+		for _, part := range parts {
+			partSum *= 10
+			partSum += int64(part)
+		}
+		logger.Println("got:  ", partSum)
+		logger.Println()
+		sum += partSum
+	}
+
+	return sum, scanner.Err()
+}