Day 02

02/main.go

@@ -0,0 +1,66 @@
+package main
+
+import (
+	"log"
+	"os"
+	"strconv"
+	"strings"
+)
+
+func main() {
+	inputBytes, _ := os.ReadFile("input.txt")
+	inputs := strings.Split(string(inputBytes), "\n")
+
+	log.Println("Puzzle 1:", puzzle1(inputs))
+	log.Println("Puzzle 2:", puzzle2(inputs))
+}
+
+func puzzle1(input []string) int {
+	// "forward X" increases the horizontal position by X units.
+	// "down X" increases the depth by X units.
+	// "up X" decreases the depth by X units.
+	horizontal := 0
+	depth := 0
+	for _, instruction := range input {
+		instructionParts := strings.Split(instruction, " ")
+		direction := instructionParts[0]
+		distance, _ := strconv.Atoi(instructionParts[1])
+		switch direction {
+		case "forward":
+			horizontal += distance
+		case "down":
+			depth += distance
+		case "up":
+			depth -= distance
+		}
+	}
+	// Multiply horizontal position and depth together to get the final answer.
+	return horizontal * depth
+}
+
+func puzzle2(input []string) int {
+	// down X increases your aim by X units.
+	// up X decreases your aim by X units.
+	// forward X does two things:
+	// - It increases your horizontal position by X units.
+	// - It increases your depth by your aim multiplied by X.
+	horizontal := 0
+	depth := 0
+	aim := 0
+	for _, instruction := range input {
+		instructionParts := strings.Split(instruction, " ")
+		direction := instructionParts[0]
+		distance, _ := strconv.Atoi(instructionParts[1])
+		switch direction {
+		case "down":
+			aim += distance
+		case "up":
+			aim -= distance
+		case "forward":
+			horizontal += distance
+			depth += aim * distance
+		}
+	}
+	// Multiply horizontal position and depth together to get the final answer.
+	return horizontal * depth
+}

02/main_test.go

@@ -0,0 +1,14 @@
+package main
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test(t *testing.T) {
+	input := `forward 5,down 5,forward 8,up 3,down 8,forward 2`
+	assert.Equal(t, 150, puzzle1(strings.Split(input, ",")))
+	assert.Equal(t, 900, puzzle2(strings.Split(input, ",")))
+}