Started AOC 2020 - solved the first 4.5 days.

2020/.gitignore

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+build/

2020/Makefile

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+all:
+
+%: %.go
+	mkdir -p build/
+	go build -o build/$@ $<
+
+clean:
+	rm -rf build/

2020/day01.go

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+package main
+
+import (
+	"fmt"
+	"os"
+
+	"git.annabunch.es/annabunches/adventofcode/2020/lib/fileutils"
+)
+
+func main() {
+	step := os.Args[1]
+	values := fileutils.InputParserIntMap(os.Args[2])
+
+	switch step {
+	case "1":
+		for x, _ := range values {
+			if _, ok := values[2020-x]; ok {
+				answer := x * (2020 - x)
+				fmt.Println("The answer is:", answer)
+				return
+			}
+		}
+	case "2":
+		for x, _ := range values {
+			target := 2020 - x
+			for y, _ := range values {
+				if _, ok := values[target-y]; ok {
+					answer := x * y * (target - y)
+					fmt.Println("The answer is:", answer)
+					return
+				}
+			}
+		}
+	}
+}

2020/day02.go

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+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"strconv"
+	"strings"
+
+	"git.annabunch.es/annabunches/adventofcode/2020/lib/fileutils"
+)
+
+func checkLine(line string, step string) int {
+	if line == "" {
+		return 0
+	}
+
+	data := strings.Split(line, " ")
+	minMaxData := strings.Split(data[0], "-")
+
+	min, err := strconv.Atoi(minMaxData[0])
+	if err != nil {
+		log.Panicf(err.Error())
+	}
+	max, err := strconv.Atoi(minMaxData[1])
+	if err != nil {
+		log.Panicf(err.Error())
+	}
+	char := strings.TrimSuffix(data[1], ":")
+
+	switch step {
+	case "1":
+		count := strings.Count(data[2], char)
+
+		if count >= min && count <= max {
+			return 1
+		}
+		return 0
+	case "2":
+		bchar := char[0]
+		if (data[2][min-1] == bchar || data[2][max-1] == bchar) &&
+			!(data[2][min-1] == bchar && data[2][max-1] == bchar) {
+			return 1
+		}
+		return 0
+	}
+
+	return 0
+}
+
+func main() {
+	step := os.Args[1]
+	values := fileutils.InputParserStrings(os.Args[2])
+
+	total := 0
+	for _, line := range values {
+		total += checkLine(line, step)
+	}
+	fmt.Println("Valid passwords:", total)
+}

2020/day03.go

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+package main
+
+import (
+	"fmt"
+	"os"
+
+	"git.annabunch.es/annabunches/adventofcode/2020/lib/fileutils"
+)
+
+func countTrees(input []string, right, down int) int {
+	x := 0
+	total := 0
+	for y, line := range input {
+		if y == 0 || len(line) == 0 || y%down != 0 {
+			continue
+		}
+
+		x = (x + right) % len(line)
+		if line[x] == '#' {
+			total += 1
+		}
+	}
+
+	return total
+}
+
+func main() {
+	step := os.Args[1]
+	values := fileutils.InputParserStrings(os.Args[2])
+
+	switch step {
+	case "1":
+		total := countTrees(values, 3, 1)
+		fmt.Println("Trees:", total)
+	case "2":
+		total := countTrees(values, 1, 1)
+		total *= countTrees(values, 3, 1)
+		total *= countTrees(values, 5, 1)
+		total *= countTrees(values, 7, 1)
+		total *= countTrees(values, 1, 2)
+		fmt.Println("Tree Product:", total)
+	}
+
+}

2020/day04.go

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+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"regexp"
+	"strconv"
+	"strings"
+
+	"git.annabunch.es/annabunches/adventofcode/2020/lib/fileutils"
+)
+
+func splitPassports(input []string) []string {
+	converted := []string{}
+
+	current := ""
+	for _, line := range input {
+		if line == "" {
+			converted = append(converted, current)
+			current = ""
+			continue
+		}
+
+		current += " " + line
+	}
+
+	return converted
+}
+
+func countValidPassports(input []string, step string) int {
+	total := 0
+	for _, line := range input {
+		if strings.Contains(line, "byr:") &&
+			strings.Contains(line, "iyr:") &&
+			strings.Contains(line, "eyr:") &&
+			strings.Contains(line, "hgt:") &&
+			strings.Contains(line, "hcl:") &&
+			strings.Contains(line, "ecl:") &&
+			strings.Contains(line, "pid:") {
+			if step == "1" {
+				total += 1
+				continue
+			}
+
+			i := validatePassport(line)
+			if i == 0 {
+				log.Printf("Failed: %s", line)
+			} else {
+				log.Printf("Passed: %s", line)
+			}
+
+			total += i
+		}
+	}
+
+	return total
+}
+
+func validatePassport(input string) int {
+	fields := strings.Split(input, " ")
+	for _, field := range fields {
+		if field == "" {
+			continue
+		}
+
+		subFields := strings.Split(field, ":")
+		if len(subFields) != 2 {
+			log.Panicf("Failed to split subfields on '%s'", field)
+		}
+		name := subFields[0]
+		value := subFields[1]
+
+		switch name {
+		case "byr":
+			ivalue := makeInt(value)
+			if ivalue < 1920 || ivalue > 2002 {
+				return 0
+			}
+		case "iyr":
+			ivalue := makeInt(value)
+			if ivalue < 2010 || ivalue > 2020 {
+				return 0
+			}
+		case "eyr":
+			ivalue := makeInt(value)
+			if ivalue < 2020 || ivalue > 2030 {
+				return 0
+			}
+		case "hgt":
+			if strings.HasSuffix(value, "cm") {
+				ivalue := makeInt(strings.TrimSuffix(value, "cm"))
+				if ivalue < 150 || ivalue > 193 {
+					return 0
+				}
+			} else if strings.HasSuffix(value, "in") {
+				ivalue := makeInt(strings.TrimSuffix(value, "in"))
+				if ivalue < 59 || ivalue > 76 {
+					return 0
+				}
+			} else {
+				return 0
+			}
+		case "hcl":
+			match, err := regexp.MatchString("^#[0-9a-f]{6}$", value)
+			if err != nil {
+				log.Panicf(err.Error())
+			}
+			if !match {
+				return 0
+			}
+		case "ecl":
+			if value != "amb" &&
+				value != "blu" &&
+				value != "brn" &&
+				value != "gry" &&
+				value != "grn" &&
+				value != "hzl" &&
+				value != "oth" {
+				return 0
+			}
+		case "pid":
+			match, err := regexp.MatchString("^[0-9]{9}$", value)
+			if err != nil {
+				log.Panicf(err.Error())
+			}
+			if !match {
+				return 0
+			}
+		case "cid":
+		default:
+			log.Panicf("Got bad field data: ")
+		}
+	}
+
+	return 1
+}
+
+func makeInt(input string) int {
+	i, err := strconv.Atoi(input)
+	if err != nil {
+		log.Panicf(err.Error())
+	}
+	return i
+}
+
+func main() {
+	step := os.Args[1]
+	values := fileutils.InputParserStrings(os.Args[2])
+	values = splitPassports(values)
+
+	fmt.Println("Valid Passports:", countValidPassports(values, step))
+}

2020/day05.go

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+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"strconv"
+	"strings"
+
+	"git.annabunch.es/annabunches/adventofcode/2020/lib/fileutils"
+)
+
+func calculateSeatNumber(input string) int {
+	if input == "" {
+		return 0
+	}
+
+	row, err := strconv.ParseInt(strings.ReplaceAll(strings.ReplaceAll(input[0:7], "F", "0"), "B", "1"), 2, 32)
+	if err != nil {
+		log.Panicf(err.Error())
+	}
+	col, err := strconv.ParseInt(strings.ReplaceAll(strings.ReplaceAll(input[7:10], "L", "0"), "R", "1"), 2, 32)
+	if err != nil {
+		log.Panicf(err.Error())
+	}
+	return int((row * 8) + col)
+}
+
+func main() {
+	step := os.Args[1]
+	values := fileutils.InputParserStrings(os.Args[2])
+
+	switch step {
+	case "1":
+		max := 0
+		for _, line := range values {
+			seatNumber := calculateSeatNumber(line)
+			if seatNumber > max {
+				max = seatNumber
+			}
+		}
+		fmt.Println("Highest Seat Number:", max)
+	case "2":
+		// build a map of all seat numbers then just print the ones between 0 and 1024 that don't exist
+	}
+}

2020/go.mod

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+module git.annabunch.es/annabunches/adventofcode/2020
+
+go 1.15

2020/lib/fileutils/fileutils.go

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+package fileutils
+
+import (
+	"bufio"
+	"io/ioutil"
+	"log"
+	"os"
+	"strconv"
+	"strings"
+)
+
+func InputParserIntMap(filename string) map[int]bool {
+	file, err := os.Open(filename)
+	defer file.Close()
+
+	if err != nil {
+		log.Panicf(err.Error())
+	}
+
+	values := make(map[int]bool)
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		x, err := strconv.Atoi(scanner.Text())
+		if err != nil {
+			log.Panicf(err.Error())
+		}
+		values[x] = true
+	}
+
+	return values
+}
+
+func InputParserStrings(filename string) []string {
+	data, err := ioutil.ReadFile(filename)
+	if err != nil {
+		log.Panicf(err.Error())
+	}
+	return strings.Split(string(data), "\n")
+}