add 2024/day5

2024/05/main.go

@@ -0,0 +1,110 @@
+package main
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+
+	"aoc/helper"
+)
+
+type rules map[[2]int]struct{}
+type updates []update
+type update []int
+
+func main() {
+	order_rules, page_updates := getOrdersAndUpdate()
+
+	// part 1
+	sum := 0
+	for _, update := range page_updates {
+		if update.validateRules(order_rules) {
+			sum += update.getMiddleNumber()
+		}
+	}
+	fmt.Printf("Summed updates: %d\n", sum)
+
+	// part 2
+	sum = 0
+	for _, update := range page_updates {
+		if update.validateRules(order_rules) {
+			continue
+		}
+
+		update.reorderByRules(order_rules)
+		if update.validateRules(order_rules) {
+			sum += update.getMiddleNumber()
+		}
+	}
+	fmt.Printf("Sum fixed updates: %d\n", sum)
+}
+
+func (u update) reorderByRules(r rules) update {
+	sort.Slice(
+		u,
+		func(i, j int) bool {
+			pair := [2]int{u[i], u[j]}
+			if _, exists := r[pair]; exists {
+				return true
+			}
+			pair = [2]int{u[j], u[i]}
+			if _, exists := r[pair]; exists {
+				return false
+			}
+			return false
+		},
+	)
+	return u
+}
+
+func (u update) validateRules(r rules) bool {
+	for i := 0; i < len(u)-1; i++ {
+		// check if a rule exists for current page pair (this + next)
+		pair := [2]int{u[i+1], u[i]}
+		if _, exists := r[pair]; exists {
+			return false
+		}
+	}
+	return true
+}
+
+func (u update) getMiddleNumber() int {
+	return u[len(u)/2]
+}
+
+func getOrdersAndUpdate() (rules, updates) {
+	data := helper.GetLines()
+
+	// parse rules
+	rules := rules{}
+	for data.Scan() {
+		line := data.Text()
+
+		if len(line) <= 1 {
+			// empty line, leave the rest for the update parser
+			break
+		}
+
+		parts := strings.Split(line, "|")
+		page := helper.ToInt(parts[0])
+		after := helper.ToInt(parts[1])
+
+		rules[[2]int{page, after}] = struct{}{}
+	}
+
+	// parse updates
+	updates := updates{}
+	for data.Scan() {
+		line := data.Text()
+		parts := strings.Split(line, ",")
+
+		update := update{}
+		for _, part := range parts {
+			update = append(update, helper.ToInt(part))
+		}
+
+		updates = append(updates, update)
+	}
+
+	return rules, updates
+}

helper/input.go

@@ -11,7 +11,7 @@ import (
 
 const INPUT_FILE = "input"
 
-func getLines() *bufio.Scanner {
+func GetLines() *bufio.Scanner {
 	wd, err := os.Getwd()
 	filePath := filepath.Join(wd, INPUT_FILE)
 
@@ -24,7 +24,7 @@ func getLines() *bufio.Scanner {
 }
 
 func ReadLinesTwoIntSlices() (list_a []int, list_b []int) {
-	scanner := getLines()
+	scanner := GetLines()
 	for scanner.Scan() {
 		parts := strings.Fields(scanner.Text())
 
@@ -39,7 +39,7 @@ func ReadLinesTwoIntSlices() (list_a []int, list_b []int) {
 }
 
 func ReadLinesToIntSlices() (lines [][]int) {
-	scanner := getLines()
+	scanner := GetLines()
 	for scanner.Scan() {
 		string_line := strings.Fields(scanner.Text())
 		int_line := make([]int, len(string_line))
@@ -53,7 +53,7 @@ func ReadLinesToIntSlices() (lines [][]int) {
 }
 
 func ReadLinesToStringSlices() (lines []string) {
-	scanner := getLines()
+	scanner := GetLines()
 	for scanner.Scan() {
 		lines = append(lines, scanner.Text())
 	}
@@ -62,7 +62,7 @@ func ReadLinesToStringSlices() (lines []string) {
 }
 
 func ReadLinesToString() (line string) {
-	scanner := getLines()
+	scanner := GetLines()
 	for scanner.Scan() {
 		line += scanner.Text()
 	}