day 1

.gitignore

@@ -15,4 +15,5 @@
 # vendor/
 
 # Other stuff
-*.log
+*.log
+input.txt

day-1/main.go

@@ -0,0 +1,111 @@
+/* Day 1: Sonar Sweep */
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strconv"
+)
+
+const DEBUG = true
+const WIDTH = 100
+
+func check(e error) {
+	if e != nil {
+		fmt.Println("Oh snap!")
+		panic(e)
+	}
+}
+
+func main() {
+	fmt.Println("--- Day 1: Sonar Sweep ---")
+	part1()
+	fmt.Println()
+
+	part2()
+	fmt.Println()
+}
+
+func part1() {
+	fmt.Println("* Part 1 *")
+	fmt.Println(" Goal: Count the number of times a depth measurement increases from the previous measurement.")
+	fmt.Println(" Answer: How many measurements are larger than the previous measurement?")
+
+	input, err := os.Open("./input.txt")
+	check(err)
+	defer input.Close()
+
+	scanner := bufio.NewScanner(input)
+
+	lastValue := -1
+	measurements := 0
+	increases := 0
+
+	for scanner.Scan() {
+		value, err := strconv.Atoi(scanner.Text())
+		check(err)
+		measurements++
+		if lastValue != -1 && lastValue < value {
+			increases++
+		}
+		printPip(lastValue, lastValue, value, measurements)
+
+		lastValue = value
+	}
+
+	fmt.Printf("\nRead %d measurements resulting in %d increases\n", measurements, increases)
+}
+
+func part2() {
+	fmt.Println("* Part 2 *")
+	fmt.Println(" Goal: Count the number of times the sum of measurements in this sliding window increases")
+	fmt.Println(" Answer: How many sums are larger than the previous sum?")
+
+	input, err := os.Open("./input.txt")
+	check(err)
+	defer input.Close()
+
+	scanner := bufio.NewScanner(input)
+
+	w1, w2, w3 := -1, -1, -1
+	measurements := 0
+	increases := 0
+
+	for scanner.Scan() {
+		value, err := strconv.Atoi(scanner.Text())
+		check(err)
+		measurements++
+
+		previous := w1 + w2 + w3
+		current := w2 + w3 + value
+
+		if w1 != -1 && current > previous {
+			increases++
+		}
+
+		printPip(w1, previous, current, measurements)
+
+		// shift over the window
+		w1, w2, w3 = w2, w3, value
+	}
+
+	fmt.Printf("\nRead %d measurements resulting in %d increases\n", measurements, increases)
+}
+
+func printPip(first int, previous int, current int, total int) {
+	if !DEBUG {
+		return
+	}
+
+	if first != -1 && current > previous {
+		fmt.Print("+")
+	} else if first != -1 && current < previous {
+		fmt.Print("-")
+	} else {
+		fmt.Print(".")
+	}
+	if total%WIDTH == 0 {
+		fmt.Println() // linebreak
+	}
+}

main.go.template

@@ -0,0 +1,37 @@
+/* Day #: */
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+)
+
+func check(e error) {
+	if e != nil {
+		fmt.Println("Oh snap!")
+		panic(e)
+	}
+}
+
+func ReadAllLines(input *os.File) []string {
+	scanner := bufio.NewScanner(input)
+	var text []string
+	for scanner.Scan() {
+		text = append(text, scanner.Text())
+	}
+	return text
+}
+
+func main() {
+
+	input1, err := os.Open("./input.txt")
+	check(err)
+
+	text := ReadAllLines(input1)
+	input1.Close()
+
+	fmt.Printf("Read %d lines from %s\n", len(text), "input.txt")
+
+	fmt.Println()
+}

makefile

@@ -1,5 +1,8 @@
-default: 0
+default: 1
 	# This is my 2021 Advent of Code project
 
-0:
+init:
+	mkdir day-$(day); sed 's/#/$(day)/' main.go.template > day-$(day)/main.go; touch day-$(day)/input.txt
+
+0 1:
 	cd day-$@; go run .