Finished day 11

2024/day11/day11.go

@@ -0,0 +1,86 @@
+package day11
+
+import (
+	"bufio"
+	"math"
+	"os"
+	"strconv"
+	"strings"
+)
+
+func update(stones map[int]int) map[int]int {
+	processed := make(map[int]int)
+	for stone, count := range stones {
+		if stone == 0 {
+			processed[1] += count
+			continue
+		}
+
+		places := int(math.Log10(float64(stone))) + 1
+		if places%2 == 0 {
+			half := places / 2
+			divisor := int(math.Pow10(half))
+
+			left := stone / divisor
+			right := stone % divisor
+
+			processed[left] += count
+			processed[right] += count
+			continue
+		}
+
+		processed[stone*2024] += count
+	}
+
+	return processed
+}
+
+func Part1(stones map[int]int, steps int) int {
+	for i := 0; i < steps; i++ {
+		stones = update(stones)
+	}
+
+	sum := 0
+	for _, count := range stones {
+		sum += count
+	}
+
+	return sum
+}
+
+func Part2(stones map[int]int, steps int) int {
+	return Part1(stones, steps)
+}
+
+func Run(filename string) (int, int) {
+	file, err := os.Open(filename)
+	if err != nil {
+		panic(err)
+	}
+	defer file.Close()
+
+	stones := make(map[int]int)
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		line := scanner.Text()
+
+		for _, c := range strings.Split(line, " ") {
+			id, err := strconv.Atoi(c)
+			if err != nil {
+				panic(err)
+			}
+
+			stones[id] += 1
+		}
+	}
+
+	if err := scanner.Err(); err != nil {
+		panic(err)
+	}
+
+	part1 := Part1(stones, 25)
+	part2 := Part2(stones, 75)
+
+	return part1, part2
+}

2024/day11/day11_test.go

@@ -0,0 +1,44 @@
+package day11
+
+import (
+	"os"
+	"testing"
+)
+
+func TestDay11(t *testing.T) {
+	filename := "test.txt"
+	if _, err := os.Stat(filename); os.IsNotExist(err) {
+		t.Fatalf("test file does not exist: %v", filename)
+	}
+
+	part1, part2 := Run(filename)
+
+	expectedPart1 := 55312
+	if part1 != expectedPart1 {
+		t.Fatalf("unexpected part1:\nwant:\t%d\ngot:\t%d", expectedPart1, part1)
+	}
+
+	expectedPart2 := 65601038650482
+	if part2 != expectedPart2 {
+		t.Fatalf("unexpected part2:\nwant:\t%d\ngot:\t%d", expectedPart2, part2)
+	}
+}
+
+func TestDay11Solution(t *testing.T) {
+	filename := "input.txt"
+	if _, err := os.Stat(filename); os.IsNotExist(err) {
+		t.Fatalf("test file does not exist: %v", filename)
+	}
+
+	part1, part2 := Run(filename)
+
+	expectedPart1 := 197157
+	if part1 != expectedPart1 {
+		t.Fatalf("unexpected part1:\nwant:\t%d\ngot:\t%d", expectedPart1, part1)
+	}
+
+	expectedPart2 := 234430066982597
+	if part2 != expectedPart2 {
+		t.Fatalf("unexpected part2:\nwant:\t%d\ngot:\t%d", expectedPart2, part2)
+	}
+}

2024/day11/input.txt

@@ -0,0 +1 @@
+0 44 175060 3442 593 54398 9 8101095

2024/day11/test.txt

@@ -0,0 +1 @@
+125 17

2024/main.go

@@ -8,6 +8,7 @@ import (
 
 	"cpatino.com/advent-of-code/2024/day1"
 	"cpatino.com/advent-of-code/2024/day10"
+	"cpatino.com/advent-of-code/2024/day11"
 	"cpatino.com/advent-of-code/2024/day2"
 	"cpatino.com/advent-of-code/2024/day3"
 	"cpatino.com/advent-of-code/2024/day4"
@@ -29,6 +30,7 @@ var days = map[int]func(string) (int, int){
 	8:  day8.Run,
 	9:  day9.Run,
 	10: day10.Run,
+	11: day11.Run,
 }
 
 func main() {