day 2, knocking off rust still

2021/day02/main.go

@@ -0,0 +1,67 @@
+package main
+
+import (
+	_ "embed"
+	"flag"
+	"fmt"
+	"strings"
+
+	"github.com/alexchao26/advent-of-code-go/cast"
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+//go:embed input.txt
+var input string
+
+func init() {
+	// do this in init (not main) so test file has same input
+	input = strings.TrimRight(input, "\n")
+	if len(input) == 0 {
+		panic("empty input.txt file")
+	}
+}
+
+func main() {
+	var part int
+	flag.IntVar(&part, "part", 1, "part 1 or 2")
+	flag.Parse()
+	fmt.Println("Running part", part)
+
+	ans := day2(input, part)
+	util.CopyToClipboard(fmt.Sprintf("%v", ans))
+	fmt.Println("Output:", ans)
+}
+
+func day2(input string, part int) int {
+	var horiz, depth int
+	var aim int
+
+	for _, line := range strings.Split(input, "\n") {
+		parts := strings.Split(line, " ")
+		dir := parts[0]
+		dist := cast.ToInt(parts[1])
+
+		if part == 1 {
+			switch dir {
+			case "down":
+				depth += dist
+			case "up":
+				depth -= dist
+			case "forward":
+				horiz += dist
+			}
+		} else {
+			switch dir {
+			case "down":
+				aim += dist
+			case "up":
+				aim -= dist
+			case "forward":
+				horiz += dist
+				depth += aim * dist
+			}
+		}
+	}
+
+	return horiz * depth
+}