From 9c221a81121ea58492675328c28ab6a91676e2d4 Mon Sep 17 00:00:00 2001
From: Stevan Freeborn <65925598+StevanFreeborn@users.noreply.github.com>
Date: Tue, 9 Dec 2025 07:09:27 -0600
Subject: [PATCH] feat: solve day 5 part 1

---
 README.md           |  2 +-
 cmd/02/rnge/rnge.go |  3 ++
 cmd/05/main.go      | 87 +++++++++++++++++++++++++++++++++++++++++++++
 cmd/05/main_test.go | 27 ++++++++++++++
 4 files changed, 118 insertions(+), 1 deletion(-)
 create mode 100644 cmd/05/main.go
 create mode 100644 cmd/05/main_test.go

diff --git a/README.md b/README.md
index 15150ae..c6b1f05 100644
--- a/README.md
+++ b/README.md
@@ -30,7 +30,7 @@ go test ./cmd/01
 | 02  | [Problem](https://adventofcode.com/2025/day/2)  | [Solution](./cmd/02/) | Part 1 should have been super straight-forward, but some whitespace screwed up my parsing of the final range. I some how was able to stumble over a solution to part 2 rather blindly.                                |
 | 03  | [Problem](https://adventofcode.com/2025/day/3)  | [Solution](./cmd/03/) | Part 1 intuitively makes you think you only care about highest nums, but then you need to consider placement. I once again tripped over the solution using a stack. However chat morally supported me the whole time. |
 | 04  | [Problem](https://adventofcode.com/2025/day/4)  | [Solution](./cmd/04/) | Part 1 was by far the most straight-forward challenge so far. This was easiest day of AoC this year by far.                                                                                                           |
-| 05  | [Problem](https://adventofcode.com/2025/day/5)  | [Solution](./cmd/05/) |                                                                                                                                                                                                                       |
+| 05  | [Problem](https://adventofcode.com/2025/day/5)  | [Solution](./cmd/05/) | Part 1 was fairly straight forward. Merging ranges was trickiest bit.                                                                                                                                                 |
 | 06  | [Problem](https://adventofcode.com/2025/day/6)  | [Solution](./cmd/06/) |                                                                                                                                                                                                                       |
 | 07  | [Problem](https://adventofcode.com/2025/day/7)  | [Solution](./cmd/07/) |                                                                                                                                                                                                                       |
 | 08  | [Problem](https://adventofcode.com/2025/day/8)  | [Solution](./cmd/08/) |                                                                                                                                                                                                                       |
diff --git a/cmd/02/rnge/rnge.go b/cmd/02/rnge/rnge.go
index 4e72d78..8e416fc 100644
--- a/cmd/02/rnge/rnge.go
+++ b/cmd/02/rnge/rnge.go
@@ -7,6 +7,9 @@ import (
 	"strings"
 )
 
+// TODO: Refactor this to separate package
+// in internal/
+
 const RangeSeparatorCharacter = "-"
 
 type Range interface {
diff --git a/cmd/05/main.go b/cmd/05/main.go
new file mode 100644
index 0000000..23830a8
--- /dev/null
+++ b/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
+}
diff --git a/cmd/05/main_test.go b/cmd/05/main_test.go
new file mode 100644
index 0000000..92f16b7
--- /dev/null
+++ b/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)
+	}
+}