solve day 1

.gitignore

@@ -0,0 +1,2 @@
+aoc-2024
+input.txt

day1.go

@@ -0,0 +1,93 @@
+package main
+
+import (
+	"fmt"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+type Day1Input struct {
+	column1 []int64
+	column2 []int64
+}
+
+func day1_parse(lines []string) (*Day1Input, error) {
+	column1 := make([]int64, len(lines))
+	column2 := make([]int64, len(lines))
+
+	for i, line := range lines {
+		parts := strings.SplitN(line, " ", 2)
+
+		column1_value, err := strconv.ParseInt(strings.TrimSpace(parts[0]), 10, 0)
+		if err != nil {
+			return nil, err
+		}
+
+
+		column2_value, err := strconv.ParseInt(strings.TrimSpace(parts[1]), 10, 0)
+		if err != nil {
+			return nil, err
+		}
+
+		column1[i] = column1_value
+		column2[i] = column2_value
+	}
+
+	parsed := Day1Input{
+		column1,
+		column2,
+	}
+
+	return &parsed, nil
+}
+
+func day1_part1(lines []string) (error) {
+	input, err := day1_parse(lines)
+	if err != nil {
+		return err
+	}
+
+	sort.Slice(input.column1, func(i, j int) bool {
+		return input.column1[i] < input.column1[j]
+	})
+
+	sort.Slice(input.column2, func(i, j int) bool {
+		return input.column2[i] < input.column2[j]
+	})
+
+	var answer int64 = 0
+	for i := range len(input.column1) {
+		if input.column1[i] > input.column2[i] {
+			answer += input.column1[i] - input.column2[i];
+		} else {
+			answer += input.column2[i] - input.column1[i];
+		}
+	}
+
+	fmt.Println(answer)
+
+	return nil
+}
+
+func day1_part2(lines []string) (error) {
+	input, err := day1_parse(lines)
+	if err != nil {
+		return err
+	}
+
+	var answer int64 = 0
+	for _, value1 := range input.column1 {
+		var count int64 = 0
+		for _, value2 := range input.column2 {
+			if value1 == value2 {
+				count += 1
+			}
+		}
+		answer += count * value1
+	}
+
+	fmt.Println(answer)
+
+	return nil
+}

go.mod

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+module aoc-2024
+
+go 1.23.2

main.go

@@ -0,0 +1,45 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"strings"
+)
+
+func showUsage() {
+	print(len(os.Args))
+	fmt.Printf("Usage: %s <day> <part> [input.txt]\n", os.Args[0])
+}
+
+func main() {
+	if (len(os.Args) < 3) {
+		showUsage()
+		return
+	}
+
+	day := os.Args[1]
+	part := os.Args[2]
+
+	var input_filename string
+	if len(os.Args) <= 3 {
+		input_filename = "input.txt"
+	} else {
+		input_filename = os.Args[3]
+	}
+
+	contents, err := os.ReadFile(input_filename)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	lines := strings.Split(strings.TrimRight(string(contents), "\n"), "\n")
+
+	if day == "1" {
+		if part == "1" {
+			day1_part1(lines)
+		} else if part == "2" {
+			day1_part2(lines)
+		}
+	}
+}