[2024] Solution for Day 5

Author: kfarnung

2024/day05/main.go

@@ -0,0 +1,160 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"slices"
+	"strings"
+
+	"github.com/kfarnung/advent-of-code/2024/lib"
+)
+
+type constraint struct {
+	first  int64
+	second int64
+}
+
+func part1(input string) int64 {
+	constraints, err := parseConstraints(input)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	pageLists, err := parsePageList(input)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	sum := int64(0)
+	for _, pages := range pageLists {
+		meetsAllConstraints := true
+		for _, constraint := range constraints {
+			firstIndex := slices.Index(pages, constraint.first)
+			secondIndex := slices.Index(pages, constraint.second)
+
+			if firstIndex == -1 || secondIndex == -1 {
+				continue
+			}
+
+			if secondIndex < firstIndex {
+				meetsAllConstraints = false
+				break
+			}
+		}
+
+		if meetsAllConstraints {
+			sum += pages[len(pages)/2]
+		}
+	}
+
+	return sum
+}
+
+func part2(input string) int64 {
+	constraints, err := parseConstraints(input)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	pageLists, err := parsePageList(input)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	sum := int64(0)
+	for _, pages := range pageLists {
+		meetsAllConstraints := true
+		didSwap := true
+		for didSwap {
+			didSwap = false
+			for _, constraint := range constraints {
+				firstIndex := slices.Index(pages, constraint.first)
+				secondIndex := slices.Index(pages, constraint.second)
+
+				if firstIndex == -1 || secondIndex == -1 {
+					continue
+				}
+
+				if secondIndex < firstIndex {
+					meetsAllConstraints = false
+
+					temp := pages[firstIndex]
+					pages[firstIndex] = pages[secondIndex]
+					pages[secondIndex] = temp
+
+					didSwap = true
+				}
+			}
+		}
+
+		if !meetsAllConstraints {
+			sum += pages[len(pages)/2]
+		}
+	}
+
+	return sum
+}
+
+func parseConstraints(input string) ([]constraint, error) {
+	var constraints []constraint
+	for _, line := range lib.SplitLines(input) {
+		if line == "" {
+			break
+		}
+
+		split := strings.Split(line, "|")
+		first, err := lib.ParseInt[int64](split[0])
+		if err != nil {
+			return nil, err
+		}
+
+		second, err := lib.ParseInt[int64](split[1])
+		if err != nil {
+			return nil, err
+		}
+
+		constraints = append(constraints, constraint{first, second})
+	}
+
+	return constraints, nil
+}
+
+func parsePageList(input string) ([][]int64, error) {
+	var pages [][]int64
+	foundBreak := false
+	for _, line := range lib.SplitLines(input) {
+		if line == "" {
+			foundBreak = true
+			continue
+		} else if !foundBreak {
+			continue
+		}
+
+		split := strings.Split(line, ",")
+		var page []int64
+		for _, s := range split {
+			val, err := lib.ParseInt[int64](s)
+			if err != nil {
+				return nil, err
+			}
+
+			page = append(page, val)
+		}
+
+		pages = append(pages, page)
+	}
+
+	return pages, 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/day05/main_test.go

@@ -0,0 +1,63 @@
+package main
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/kfarnung/advent-of-code/2024/lib"
+	"github.com/stretchr/testify/assert"
+)
+
+var input = strings.Join([]string{
+	"47|53",
+	"97|13",
+	"97|61",
+	"97|47",
+	"75|29",
+	"61|13",
+	"75|53",
+	"29|13",
+	"97|29",
+	"53|29",
+	"61|53",
+	"97|53",
+	"61|29",
+	"47|13",
+	"75|47",
+	"97|75",
+	"47|61",
+	"75|61",
+	"47|29",
+	"75|13",
+	"53|13",
+	"",
+	"75,47,61,53,29",
+	"97,61,53,29,13",
+	"75,29,13",
+	"75,97,47,61,53",
+	"61,13,29",
+	"97,13,75,29,47",
+	"",
+}, "\n")
+
+func TestPart1(t *testing.T) {
+	assert.Equal(t, int64(143), part1(input))
+
+	inputContent, err := lib.GetInputContent()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assert.Equal(t, int64(6041), part1(inputContent))
+}
+
+func TestPart2(t *testing.T) {
+	assert.Equal(t, int64(123), part2(input))
+
+	inputContent, err := lib.GetInputContent()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assert.Equal(t, int64(4884), part2(inputContent))
+}