feat: solve part one

internal/2017/DayThree/code.go

@@ -0,0 +1,50 @@
+package daythree
+
+import (
+	"advent-of-code/internal/registry"
+	"os"
+	"strconv"
+)
+
+func init() {
+	registry.Register("2017D3", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) int {
+	content, _ := os.ReadFile(filepath)
+	data, _ := strconv.Atoi(string(content))
+	return data
+}
+
+func abs(n int) int {
+	if n < 0 {
+		return -n
+	}
+	return n
+}
+
+func PartOne(data int) int {
+	layer := 1
+
+	for (2*layer+1)*(2*layer+1) < data {
+		layer++
+	}
+
+	sideLength := 2*layer + 1
+	offset := sideLength*sideLength - data
+	side := offset / (sideLength - 1)
+	position := offset % (sideLength - 1)
+
+	coordinates := [4][2]int{
+		{layer, layer - position},
+		{layer - position, -layer},
+		{-layer, -layer + position},
+		{-layer + position, layer},
+	}
+
+	return abs(coordinates[side][0]) + abs(coordinates[side][1])
+}
+
+func PartTwo(data int) int {
+	return 0
+}