feat: add part one solution

internal/2015/DayThree/code.go

@@ -0,0 +1,43 @@
+package daythree
+
+import (
+	"advent-of-code/internal/registry"
+	"os"
+)
+
+type coordinates struct {
+	x, y int
+}
+
+func init() {
+	registry.Register("2015D3", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) string {
+	content, _ := os.ReadFile(filepath)
+	return string(content)
+}
+
+func PartOne(data string) int {
+	houses := make(map[coordinates]int)
+	x, y := 0, 0
+	houses[coordinates{x, y}] = 1
+	for _, direction := range data {
+		switch direction {
+		case '>':
+			x++
+		case '<':
+			x--
+		case '^':
+			y++
+		case 'v':
+			y--
+		}
+		houses[coordinates{x, y}]++
+	}
+	return len(houses)
+}
+
+func PartTwo(data string) int {
+	return 0
+}