add day 2 results

day-2/main.go

@@ -0,0 +1,111 @@
+/* Day 2: Dive! */
+package main
+
+import (
+	"AoC2021/utils/timer"
+	"bufio"
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+)
+
+func check(e error) {
+	if e != nil {
+		fmt.Println("Oh snap!")
+		panic(e)
+	}
+}
+
+func main() {
+	fmt.Println("--- Day 2: Dive! ---")
+	timer.Start()
+	part1()
+	timer.Tick()
+	fmt.Println()
+
+	part2()
+	timer.Tick()
+	fmt.Println()
+}
+
+func part1() {
+	fmt.Println("* Part 1 *")
+	fmt.Println(" Goal: Calculate the horizontal position and depth you would have after following the planned course")
+	fmt.Println(" Answer: What do you get if you multiply your final horizontal position by your final depth?")
+
+	input, err := os.Open("./input.txt")
+	defer input.Close()
+	check(err)
+
+	scanner := bufio.NewScanner(input)
+	lines := 0
+	posX, posY := 0, 0
+
+	for scanner.Scan() {
+		str := scanner.Text()
+		values := strings.Fields(str)
+		if len(values) < 2 {
+			panic("read invalid line: " + str)
+		}
+		direction := values[0]
+		units, err := strconv.Atoi(values[1])
+		check(err)
+		switch direction {
+		case "forward":
+			posX += units
+		case "down":
+			posY += units
+		case "up":
+			posY -= units
+		default:
+			panic("Invalid direction: " + direction)
+		}
+
+		lines++
+	}
+
+	fmt.Printf("Read %d lines from input\n", lines)
+	fmt.Printf("The final position is (%d, %d) for an answer of %d\n", posX, posY, posX*posY)
+}
+
+func part2() {
+	fmt.Println("* Part 2 *")
+	fmt.Println(" Goal: Using this new interpretation of the commands, calculate the horizontal position and depth you would have after following the planned course")
+	fmt.Println(" Answer: What do you get if you multiply your final horizontal position by your final depth?")
+
+	input, err := os.Open("./input.txt")
+	defer input.Close()
+	check(err)
+
+	scanner := bufio.NewScanner(input)
+	lines := 0
+	posX, posY, aim := 0, 0, 0
+
+	for scanner.Scan() {
+		str := scanner.Text()
+		values := strings.Fields(str)
+		if len(values) < 2 {
+			panic("read invalid line: " + str)
+		}
+		direction := values[0]
+		units, err := strconv.Atoi(values[1])
+		check(err)
+		switch direction {
+		case "forward":
+			posX += units
+			posY += units * aim
+		case "down":
+			aim += units
+		case "up":
+			aim -= units
+		default:
+			panic("Invalid direction: " + direction)
+		}
+
+		lines++
+	}
+
+	fmt.Printf("Read %d lines from input\n", lines)
+	fmt.Printf("The final position is (%d, %d) for an answer of %d\n", posX, posY, posX*posY)
+}