Merge pull request #3 from StevanFreeborn/stevanfreeborn/feat/solve-day-two-part-one

feat: solve day 2 part 1

README.md

@@ -23,7 +23,7 @@ Each day's solution is contained in a separate package.
 | Day | Problem                                         | Solution              | Notes                                                                                                                                                             |
 |-----|-------------------------------------------------|-----------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------|
 | 01  | [Problem](https://adventofcode.com/2025/day/1)  | [Solution](./cmd/01/) | Part 1 seemed straight forward enough. Part 2 completely stumped me. The trickiest part was not counting zero's twice when you ended and then started from there. |
-| 02  | [Problem](https://adventofcode.com/2025/day/2)  | [Solution](./cmd/02/) |                                                                                                                                                                   |
+| 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.                                                     |
 | 03  | [Problem](https://adventofcode.com/2025/day/3)  | [Solution](./cmd/03/) |                                                                                                                                                                   |
 | 04  | [Problem](https://adventofcode.com/2025/day/4)  | [Solution](./cmd/04/) |                                                                                                                                                                   |
 | 05  | [Problem](https://adventofcode.com/2025/day/5)  | [Solution](./cmd/05/) |                                                                                                                                                                   |

cmd/02/main.go

@@ -0,0 +1,64 @@
+package main
+
+import (
+	"os"
+	"strconv"
+	"strings"
+)
+
+const SeparatorCharacter = ","
+const RangeSeparatorCharacter = "-"
+
+type Range struct {
+	Start int64
+	End   int64
+}
+
+func SolvePartOne(filePath string) int64 {
+	bytes, readErr := os.ReadFile(filePath)
+
+	if readErr != nil {
+		return 0
+	}
+
+	strRanges := strings.SplitSeq(string(bytes), SeparatorCharacter)
+
+	rngs := []Range{}
+
+	for r := range strRanges {
+		parts := strings.Split(strings.TrimSpace(r), "-")
+		start, _ := strconv.ParseInt(parts[0], 10, 64)
+		end, _ := strconv.ParseInt(parts[1], 10, 64)
+		rng := Range{
+			Start: start,
+			End:   end,
+		}
+		rngs = append(rngs, rng)
+	}
+
+	total := int64(0)
+
+	for _, rng := range rngs {
+		for id := rng.Start; id <= rng.End; id++ {
+			idStr := strconv.FormatInt(id, 10)
+			idLength := len(idStr)
+
+			if idLength%2 != 0 {
+				continue
+			}
+
+			midpoint := idLength / 2
+
+			firstHalf := idStr[:midpoint]
+			secondHalf := idStr[midpoint:]
+
+			if firstHalf != secondHalf {
+				continue
+			}
+
+			total += id
+		}
+	}
+
+	return total
+}

cmd/02/main_test.go

@@ -0,0 +1,27 @@
+package main_test
+
+import (
+	"testing"
+
+	solution "github.com/StevanFreeborn/advent-of-code-2025/cmd/02"
+)
+
+func TestSolvePartOneWithExampleInput(t *testing.T) {
+	expected := int64(1_227_775_554)
+
+	result := solution.SolvePartOne("EXAMPLE.txt")
+
+	if result != expected {
+		t.Errorf("expected %d, got %d", expected, result)
+	}
+}
+
+func TestSolvePartOneWithInput(t *testing.T) {
+	expected := int64(18_952_700_150)
+
+	result := solution.SolvePartOne("INPUT.txt")
+
+	if result != expected {
+		t.Errorf("expected %d, got %d", expected, result)
+	}
+}