Day05

2024/gareth/day05/day05.go

@@ -0,0 +1,134 @@
+package day05
+
+import (
+	"strconv"
+	"strings"
+)
+
+type Rule struct {
+	X, Y int
+}
+
+func ParseInput(input string) ([]Rule, [][]int) {
+	sections := strings.Split(input, "\n\n")
+
+	ruleLines := strings.Split(strings.TrimSpace(sections[0]), "\n")
+	var rules []Rule
+	for _, ruleLine := range ruleLines {
+		parts := strings.Split(ruleLine, "|")
+		x, _ := strconv.Atoi(parts[0])
+		y, _ := strconv.Atoi(parts[1])
+		rules = append(rules, Rule{X: x, Y: y})
+	}
+
+	updateLines := strings.Split(strings.TrimSpace(sections[1]), "\n")
+	var updates [][]int
+	for _, updateLine := range updateLines {
+		parts := strings.Split(updateLine, ",")
+		var update []int
+		for _, part := range parts {
+			page, _ := strconv.Atoi(part)
+			update = append(update, page)
+		}
+		updates = append(updates, update)
+	}
+
+	return rules, updates
+}
+
+func ValidateUpdate(update []int, rules []Rule) bool {
+	indexMap := make(map[int]int)
+	for i, page := range update {
+		indexMap[page] = i
+	}
+
+	for _, rule := range rules {
+		pageX, indexX := indexMap[rule.X]
+		pageY, indexY := indexMap[rule.Y]
+		if indexX && indexY && pageX > pageY {
+			return false
+		}
+	}
+
+	return true
+}
+
+func FindMiddle(update []int) int {
+	n := len(update)
+	return update[n/2]
+}
+
+func SortUpdate(update []int, rules []Rule) []int {
+	depen := make(map[int][]int)
+	for _, rule := range rules {
+		depen[rule.Y] = append(depen[rule.Y], rule.X)
+	}
+
+	visited := make(map[int]bool)
+	var sorted []int
+
+	for _, page := range update {
+		if !visited[page] {
+			sorted = Visit(page, depen, visited, update, sorted)
+		}
+	}
+
+	return sorted
+}
+
+func Visit(page int, depen map[int][]int, visited map[int]bool, update []int, sorted []int) []int {
+	if visited[page] {
+		return sorted
+	}
+	visited[page] = true
+
+	for _, d := range depen[page] {
+		if contains(update, d) {
+			sorted = Visit(d, depen, visited, update, sorted)
+		}
+	}
+
+	sorted = append(sorted, page)
+	return sorted
+}
+
+func contains(slice []int, element int) bool {
+	for _, item := range slice {
+		if item == element {
+			return true
+		}
+	}
+	return false
+}
+
+func Part1(input string) int {
+	rules, updates := ParseInput(input)
+	total := 0
+
+	for _, update := range updates {
+		if ValidateUpdate(update, rules) {
+			total += FindMiddle(update)
+		}
+	}
+
+	return total
+}
+
+func Part2(input string) int {
+	rules, updates := ParseInput(input)
+	var invalidUpdates [][]int
+	total := 0
+
+	for _, update := range updates {
+		if !ValidateUpdate(update, rules) {
+			invalidUpdates = append(invalidUpdates, update)
+		}
+	}
+
+	for _, update := range invalidUpdates {
+		sortedUpdate := SortUpdate(update, rules)
+		total += FindMiddle(sortedUpdate)
+	}
+
+	return total
+}

2024/gareth/day05/day05_test.go

@@ -0,0 +1,71 @@
+package day05
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestPart1(t *testing.T) {
+	r := Part1(`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`)
+	assert.Equal(t, 143, r)
+}
+
+func TestPart2(t *testing.T) {
+	r := Part2(`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`)
+	assert.Equal(t, 123, r)
+}

2024/gareth/main.go

@@ -1,13 +1,13 @@
 package main
 
 import (
-	"aoc2024/day03"
+	"aoc2024/day05"
 	"fmt"
 	"os"
 )
 
 func main() {
-	data, _ := os.ReadFile("day03/input.txt")
-	fmt.Printf("part 1: %d\n", day03.Part1(string(data)))
-	fmt.Printf("part 2: %d\n", day03.Part2(string(data)))
+	data, _ := os.ReadFile("day05/input.txt")
+	fmt.Printf("part 1: %d\n", day05.Part1(string(data)))
+	fmt.Printf("part 2: %d\n", day05.Part2(string(data)))
 }