[2024] Solution for Day 1

Author: kfarnung

.github/workflows/2024.yml

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+name: Advent of Code 2024
+
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - .github/workflows/2024.yml
+      - 2024/**
+  pull_request:
+    paths:
+      - .github/workflows/2024.yml
+      - 2024/**
+
+jobs:
+  build-2024:
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: "2024"
+
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          token: ${{ secrets.PAT }}
+          submodules: true
+
+      - uses: actions/setup-go@v2
+        with:
+          go-version: ^1.19
+
+      - name: Get dependencies
+        run: go get -v -t -d ./...
+
+      - name: Build
+        run: go build -v ./...
+
+      - name: Test
+        run: go test -v ./...

2024/README.md

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+# Advent of Code 2024
+
+https://adventofcode.com/2024
+
+## Language
+
+Implemented in [Go](https://golang.org/).
+
+## Preparation
+
+Install [Go](https://golang.org/doc/install) for your platform.
+
+## Running tests
+
+Run tests with `go test`:
+
+```console
+go test ./...
+```

2024/day01/main.go

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+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"strings"
+
+	"github.com/kfarnung/advent-of-code/2020/lib"
+)
+
+func part1(input string) int64 {
+	first, second, err := parseInput(input)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	lib.SortSliceInt64(first)
+	lib.SortSliceInt64(second)
+
+	sum := int64(0)
+	for i := 0; i < len(first); i++ {
+		sum += lib.AbsInt64(first[i] - second[i])
+	}
+
+	return sum
+}
+
+func part2(input string) int64 {
+	first, second, err := parseInput(input)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	sum := int64(0)
+	for _, value := range first {
+		count := int64(0)
+		for _, otherValue := range second {
+			if value == otherValue {
+				count++
+			}
+		}
+
+		sum += value * count
+	}
+
+	return sum
+}
+
+func parseInput(input string) ([]int64, []int64, error) {
+	var first []int64
+	var second []int64
+	lines := lib.SplitLines(input)
+	for _, line := range lines {
+		if (len(line)) == 0 {
+			continue
+		}
+
+		splitLine := strings.Split(line, " ")
+		firstValue, err := lib.ParseInt64(splitLine[0])
+		if err != nil {
+			return nil, nil, err
+		}
+
+		secondValue, err := lib.ParseInt64(splitLine[len(splitLine)-1])
+		if err != nil {
+			return nil, nil, err
+		}
+
+		first = append(first, firstValue)
+		second = append(second, secondValue)
+	}
+
+	return first, second, nil
+}
+
+func main() {
+	name := os.Args[1]
+	content, err := lib.LoadFileContent(name)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Printf("Part 1: %d\n", part1(content))
+	fmt.Printf("Part 2: %d\n", part2(content))
+}

2024/day01/main_test.go

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+package main
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/kfarnung/advent-of-code/2020/lib"
+	"github.com/stretchr/testify/assert"
+)
+
+var input string = strings.Join([]string{
+	"3   4",
+	"4   3",
+	"2   5",
+	"1   3",
+	"3   9",
+	"3   3",
+}, "\n")
+
+func TestPart1(t *testing.T) {
+	assert.Equal(t, int64(11), part1(input))
+
+	inputContent, err := lib.GetInputContent()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assert.Equal(t, int64(1603498), part1(inputContent))
+}
+
+func TestPart2(t *testing.T) {
+	assert.Equal(t, int64(31), part2(input))
+
+	inputContent, err := lib.GetInputContent()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assert.Equal(t, int64(25574739), part2(inputContent))
+}

2024/go.mod

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+module github.com/kfarnung/advent-of-code/2020
+
+go 1.19
+
+require github.com/stretchr/testify v1.10.0
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

2024/go.sum

@@ -0,0 +1,10 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
+github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

2024/lib/input.go

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+package lib
+
+import (
+	"os"
+	"strings"
+)
+
+func LoadFileContent(name string) (string, error) {
+	content, err := os.ReadFile(name)
+	if err != nil {
+		return "", err
+	}
+
+	return string(content), nil
+}
+
+func SplitLines(input string) []string {
+	return strings.Split(input, "\n")
+}

2024/lib/intmath.go

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+package lib
+
+// AbsInt64 calculates the absolute value of a given int
+func AbsInt64(n int64) int64 {
+	if n < 0 {
+		return -n
+	}
+
+	return n
+}
+
+// ModInt64 calculates the modulus value (as opposed to the remainder)
+// https://github.com/golang/go/issues/448
+func ModInt64(x, y int64) int64 {
+	return ((x % y) + y) % y
+}

2024/lib/parse.go

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+package lib
+
+import "strconv"
+
+// ParseInt32 parses the string as a base-10 int
+func ParseInt32(text string) (int32, error) {
+	value, err := strconv.ParseInt(text, 10, 32)
+	if err != nil {
+		return 0, err
+	}
+
+	return int32(value), nil
+}
+
+// ParseInt64 parses the string as a base-10 int64
+func ParseInt64(text string) (int64, error) {
+	return strconv.ParseInt(text, 10, 64)
+}

2024/lib/point2d.go

@@ -0,0 +1,49 @@
+package lib
+
+import "fmt"
+
+// Point2D represents a point in 2D space
+type Point2D struct {
+	X, Y int64
+}
+
+// NewPoint2D intitializes a Point2D struct
+func NewPoint2D(x, y int64) Point2D {
+	return Point2D{
+		X: x,
+		Y: y,
+	}
+}
+
+// Add to the coordinates of the point
+func (p *Point2D) Add(x, y int64) {
+	p.X += x
+	p.Y += y
+}
+
+// Rotate90DegreesClockwise rotates the point 90 degrees clockwise about the origin
+func (p *Point2D) Rotate90DegreesClockwise(count int) {
+	for i := 0; i < count; i++ {
+		x := p.X
+		p.X = p.Y
+		p.Y = -x
+	}
+}
+
+// Rotate90DegreesCounterClockwise rotates the point 90 degrees counter-clockwise about the origin
+func (p *Point2D) Rotate90DegreesCounterClockwise(count int) {
+	for i := 0; i < count; i++ {
+		x := p.X
+		p.X = -p.Y
+		p.Y = x
+	}
+}
+
+// ManhattanDistance calculates the manhattan distance between two points
+func (p Point2D) ManhattanDistance(other Point2D) int64 {
+	return AbsInt64(other.X-p.X) + AbsInt64(other.Y-p.Y)
+}
+
+func (p Point2D) String() string {
+	return fmt.Sprintf("(%d, %d)", p.X, p.Y)
+}