add 2nd december solution

pkg/two/two.go

@@ -0,0 +1,92 @@
+package two
+
+import (
+	"bufio"
+	"fmt"
+	"log"
+	"os"
+	"strconv"
+	"strings"
+)
+
+var depth int = 0
+var horizontalPosition int = 0
+var aim int = 0
+
+func Run() {
+	commands := readInput()
+	for _, v := range commands {
+		command := strings.Split(v, " ")
+		switch command[0] {
+		case "forward":
+			i, _ := strconv.Atoi(command[1])
+			forward(i, false)
+		case "up":
+			i, _ := strconv.Atoi(command[1])
+			up(i, false)
+		case "down":
+			i, _ := strconv.Atoi(command[1])
+			down(i, false)
+		}
+	}
+	fmt.Printf("1st final position: %d\n", horizontalPosition*depth)
+
+	depth = 0
+	horizontalPosition = 0
+
+	for _, v := range commands {
+		command := strings.Split(v, " ")
+		switch command[0] {
+		case "forward":
+			i, _ := strconv.Atoi(command[1])
+			forward(i, true)
+		case "up":
+			i, _ := strconv.Atoi(command[1])
+			up(i, true)
+		case "down":
+			i, _ := strconv.Atoi(command[1])
+			down(i, true)
+		}
+	}
+	fmt.Printf("2nd final position: %d\n", horizontalPosition*depth)
+}
+
+func up(d int, alt bool) {
+	if !alt {
+		depth -= d
+	} else {
+		aim -= d
+	}
+}
+
+func down(d int, alt bool) {
+	if !alt {
+		depth += d
+	} else {
+		aim += d
+	}
+}
+
+func forward(d int, alt bool) {
+	horizontalPosition += d
+	if alt {
+		depth += aim * d
+	}
+}
+
+func readInput() []string {
+	file, err := os.Open("./pkg/two/input.txt")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer file.Close()
+	commands := make([]string, 0)
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		commands = append(commands, scanner.Text())
+	}
+	if err := scanner.Err(); err != nil {
+		log.Fatal(err)
+	}
+	return commands
+}