feat: solve part one

internal/2025/DayNine/code.go

@@ -0,0 +1,63 @@
+package daynine
+
+import (
+	"advent-of-code/internal/registry"
+	"os"
+	"strconv"
+	"strings"
+)
+
+func init() {
+	registry.Register("2025D9", ParseInput, PartOne, PartTwo)
+}
+
+type Point struct {
+	x, y int
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(string(content), "\n")
+}
+
+func parsePoints(data []string) []Point {
+	points := make([]Point, 0, len(data))
+	for _, line := range data {
+		parts := strings.Split(line, ",")
+		x, _ := strconv.Atoi(parts[0])
+		y, _ := strconv.Atoi(parts[1])
+		points = append(points, Point{x: x, y: y})
+	}
+	return points
+}
+
+func abs(x int) int {
+	if x < 0 {
+		return -x
+	}
+	return x
+}
+
+func PartOne(data []string) int {
+	points := parsePoints(data)
+	maxArea := 0
+
+	for i := range points {
+		for j := 1; j < len(points); j++ {
+			distanceX := abs(points[i].x - points[j].x)
+			distanceY := abs(points[i].y - points[j].y)
+
+			if distanceX > 0 && distanceY > 0 {
+				area := (distanceX + 1) * (distanceY + 1)
+				if area > maxArea {
+					maxArea = area
+				}
+			}
+		}
+	}
+	return maxArea
+}
+
+func PartTwo(data []string) int {
+	return 0
+}