feat: solve day 5 part 1

cmd/05/main.go

@@ -0,0 +1,87 @@
+package main
+
+import (
+	"cmp"
+	"math"
+	"slices"
+	"strconv"
+	"strings"
+
+	"github.com/StevanFreeborn/advent-of-code-2025/internal/file"
+)
+
+const RangeSeparatorCharacter = "-"
+
+type rnge struct {
+	start int64
+	end   int64
+}
+
+func NewRange(rngeStr string) rnge {
+	parts := strings.Split(strings.TrimSpace(rngeStr), RangeSeparatorCharacter)
+	start, _ := strconv.ParseInt(parts[0], 10, 64)
+	end, _ := strconv.ParseInt(parts[1], 10, 64)
+
+	return rnge{
+		start: start,
+		end:   end,
+	}
+}
+
+func SolvePartOne(filePath string) int {
+	input := file.ReadAllLines(filePath)
+
+	parseIds := false
+
+	ids := []int64{}
+	ranges := []rnge{}
+
+	for _, line := range input {
+		if line == "" {
+			parseIds = true
+		}
+
+		if parseIds {
+			id, _ := strconv.ParseInt(line, 10, 64)
+			ids = append(ids, id)
+			continue
+		}
+
+		rnge := NewRange(line)
+		ranges = append(ranges, rnge)
+	}
+
+	slices.SortFunc(ranges, func(a rnge, b rnge) int {
+		return cmp.Compare(a.start, b.start)
+	})
+
+	mergedRanges := []rnge{
+		ranges[0],
+	}
+
+	for _, currentRange := range ranges {
+		lastMergedRange := mergedRanges[len(mergedRanges)-1]
+
+		if currentRange.start > lastMergedRange.end {
+			mergedRanges = append(mergedRanges, currentRange)
+			continue
+		}
+
+		lastMergedRange.end = int64(math.Max(float64(lastMergedRange.end), float64(currentRange.end)))
+		mergedRanges[len(mergedRanges)-1] = lastMergedRange
+	}
+
+	total := 0
+
+	for _, id := range ids {
+		for _, rnge := range ranges {
+			if id >= rnge.start && id <= rnge.end {
+				total++
+				break
+			}
+		}
+
+	}
+
+	return total
+}

cmd/05/main_test.go

@@ -0,0 +1,27 @@
+package main_test
+
+import (
+	"testing"
+
+	solution "github.com/StevanFreeborn/advent-of-code-2025/cmd/05"
+)
+
+func TestSolvePartOneWithExampleInput(t *testing.T) {
+	expected := 3
+
+	result := solution.SolvePartOne("EXAMPLE.txt")
+
+	if result != expected {
+		t.Errorf("SolvePartOne with example input: expected %d, got %d", expected, result)
+	}
+}
+
+func TestSolvePartOneWithInput(t *testing.T) {
+	expected := 643
+
+	result := solution.SolvePartOne("INPUT.txt")
+
+	if result != expected {
+		t.Errorf("SolvePartOne with input: expected %d, got %d", expected, result)
+	}
+}