[2024] Solution for Day 12 Part 1

Author: kfarnung

2024/day12/main.go

@@ -0,0 +1,109 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+
+	"github.com/kfarnung/advent-of-code/2024/lib"
+)
+
+type point struct {
+	x, y int
+}
+
+func part1(input string) int64 {
+	garden := parseInput(input)
+
+	sum := int64(0)
+	seen := make(map[point]bool)
+
+	for i, row := range garden {
+		for j := range row {
+			location := point{i, j}
+			if seen[location] {
+				continue
+			}
+
+			area, perimeter := findAreaAndPerimeter(garden, i, j, seen)
+			sum += area * perimeter
+		}
+	}
+
+	return sum
+}
+
+func part2(_ string) int64 {
+	return int64(0)
+}
+
+func findAreaAndPerimeter(garden [][]rune, i, j int, seen map[point]bool) (int64, int64) {
+	area := int64(0)
+	perimeter := int64(0)
+	region := garden[i][j]
+
+	var queue []point
+	queue = append(queue, point{x: i, y: j})
+
+	for len(queue) > 0 {
+		current := queue[0]
+		queue = queue[1:]
+
+		if seen[current] {
+			continue
+		}
+
+		seen[current] = true
+		area++
+
+		if current.x > 0 && garden[current.x-1][current.y] == region {
+			queue = append(queue, point{x: current.x - 1, y: current.y})
+		} else {
+			perimeter++
+		}
+
+		if current.x < len(garden)-1 && garden[current.x+1][current.y] == region {
+			queue = append(queue, point{x: current.x + 1, y: current.y})
+		} else {
+			perimeter++
+		}
+
+		if current.y > 0 && garden[current.x][current.y-1] == region {
+			queue = append(queue, point{x: current.x, y: current.y - 1})
+		} else {
+			perimeter++
+		}
+
+		if current.y < len(garden[0])-1 && garden[current.x][current.y+1] == region {
+			queue = append(queue, point{x: current.x, y: current.y + 1})
+		} else {
+			perimeter++
+		}
+	}
+
+	return area, perimeter
+}
+
+func parseInput(input string) [][]rune {
+	var data [][]rune
+	for _, line := range lib.SplitLines(input) {
+		if len(line) == 0 {
+			continue
+		}
+
+		data = append(data, []rune(line))
+	}
+
+	return data
+}
+
+func main() {
+	name := os.Args[1]
+	content, err := lib.LoadFileContent(name)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Printf("Part 1: %d\n", part1(content))
+	fmt.Printf("Part 2: %d\n", part2(content))
+}

2024/day12/main_test.go

@@ -0,0 +1,45 @@
+package main
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/kfarnung/advent-of-code/2024/lib"
+	"github.com/stretchr/testify/assert"
+)
+
+var input = strings.Join([]string{
+	"RRRRIICCFF",
+	"RRRRIICCCF",
+	"VVRRRCCFFF",
+	"VVRCCCJFFF",
+	"VVVVCJJCFE",
+	"VVIVCCJJEE",
+	"VVIIICJJEE",
+	"MIIIIIJJEE",
+	"MIIISIJEEE",
+	"MMMISSJEEE",
+	"",
+}, "\n")
+
+func TestPart1(t *testing.T) {
+	assert.Equal(t, int64(1930), part1(input))
+
+	inputContent, err := lib.GetInputContent()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assert.Equal(t, int64(1489582), part1(inputContent))
+}
+
+func TestPart2(t *testing.T) {
+	assert.Equal(t, int64(0), part2(input))
+
+	inputContent, err := lib.GetInputContent()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assert.Equal(t, int64(0), part2(inputContent))
+}