2024, day 5

Author: lucianoq

2024/5/Makefile

@@ -0,0 +1,20 @@
+input:
+	http "https://adventofcode.com/2024/day/5/input" "Cookie:session=${AOC_SESSION};" >input
+
+main1:
+	go build -o main1 main1.go
+
+main2:
+	go build -o main2 main2.go
+
+.PHONY: run1 run2 clean
+
+run1: main1 input
+	./main1 <input
+
+run2: main2 input
+	./main2 <input
+
+clean:
+	rm -f main1 main2 input
+

2024/5/common.go

@@ -0,0 +1,48 @@
+package main
+
+import (
+	"bufio"
+	"os"
+	"strings"
+
+	"github.com/lucianoq/container/set"
+)
+
+func parseInput() ([][]string, func(a, b string) int) {
+	scanner := bufio.NewScanner(os.Stdin)
+
+	lessThan := map[string]set.Set[string]{}
+
+	for scanner.Scan() {
+		line := scanner.Text()
+		if line == "" {
+			break
+		}
+		ff := strings.Split(line, "|")
+		if lessThan[ff[0]] == nil {
+			lessThan[ff[0]] = set.New[string]()
+		}
+		lessThan[ff[0]].Add(ff[1])
+	}
+
+	updates := [][]string{}
+	for scanner.Scan() {
+		updates = append(updates, strings.Split(scanner.Text(), ","))
+	}
+
+	// slices.SortFunc
+	cmpFn := func(a, b string) int {
+		if lessThan[a].Contains(b) {
+			return -1
+		}
+		if lessThan[b].Contains(b) {
+			return 1
+		}
+		// 0 doesn't necessarily mean they're equal, but
+		// as slices.SortFunc documentation says:
+		// | The function should return 0 for incomparable items.
+		return 0
+	}
+
+	return updates, cmpFn
+}

2024/5/main1.go

@@ -0,0 +1,21 @@
+package main
+
+import (
+	"fmt"
+	"slices"
+	"strconv"
+)
+
+func main() {
+	updates, cmpFn := parseInput()
+
+	sum := 0
+	for _, u := range updates {
+		if slices.IsSortedFunc(u, cmpFn) {
+			n, _ := strconv.Atoi(u[len(u)/2])
+			sum += n
+		}
+	}
+
+	fmt.Println(sum)
+}

2024/5/main2.go

@@ -0,0 +1,22 @@
+package main
+
+import (
+	"fmt"
+	"slices"
+	"strconv"
+)
+
+func main() {
+	updates, cmpFn := parseInput()
+
+	sum := 0
+	for _, u := range updates {
+		if !slices.IsSortedFunc(u, cmpFn) {
+			slices.SortFunc(u, cmpFn)
+			n, _ := strconv.Atoi(u[len(u)/2])
+			sum += n
+		}
+	}
+
+	fmt.Println(sum)
+}