feat: solve part one using binary search on sorted range

internal/2025/DayFive/code.go

@@ -0,0 +1,79 @@
+package dayfive
+
+import (
+	"os"
+	"slices"
+	"sort"
+	"strconv"
+	"strings"
+
+	"advent-of-code/internal/registry"
+)
+
+type freshRange struct {
+	start int
+	end   int
+}
+
+func init() {
+	registry.Register("2025D5", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(string(content), "\n")
+}
+
+func PartOne(input []string) int {
+	var freshRanges []freshRange
+	var ingredientIDs []int
+	separatorFound := false
+
+	for _, line := range input {
+		if line == "" {
+			separatorFound = true
+			continue
+		}
+
+		if !separatorFound {
+			startStr, endStr, _ := strings.Cut(line, "-")
+			start, _ := strconv.Atoi(startStr)
+			end, _ := strconv.Atoi(endStr)
+			freshRanges = append(freshRanges, freshRange{start: start, end: end})
+		} else {
+			id, _ := strconv.Atoi(line)
+			ingredientIDs = append(ingredientIDs, id)
+		}
+	}
+
+	slices.SortFunc(freshRanges, func(a, b freshRange) int {
+		switch {
+		case a.start < b.start:
+			return -1
+		case a.start > b.start:
+			return 1
+		default:
+			return 0
+		}
+	})
+
+	freshCount := 0
+	for _, id := range ingredientIDs {
+		idx := sort.Search(len(freshRanges), func(idx int) bool {
+			return freshRanges[idx].start > id
+		})
+
+		for i := idx - 1; i >= 0 && freshRanges[i].start <= id; i-- {
+			if id <= freshRanges[i].end {
+				freshCount++
+				break
+			}
+		}
+	}
+
+	return freshCount
+}
+
+func PartTwo(input []string) int {
+	return 0
+}