feat: unify invalid checks with exactTwo boolean parameter

internal/2025/DayTwo/code.go

@@ -1,24 +1,34 @@
 package daytwo
 
 import (
-	"advent-of-code/internal/registry"
 	"os"
 	"strconv"
 	"strings"
+
+	"advent-of-code/internal/registry"
 )
 
 func init() {
 	registry.Register("2025D2", ParseInput, PartOne, PartTwo)
 }
 
-func isInvalidID(id int) bool {
+func isInvalid(id int, exactTwo bool) bool {
 	sID := strconv.Itoa(id)
-	if len(sID)%2 != 0 {
-		return false
-	}
+	if exactTwo {
 		half := len(sID) / 2
 		return sID[:half] == sID[half:]
 	}
+	for patternLength := 1; patternLength <= len(sID)/2; patternLength++ {
+		repetitions := len(sID) / patternLength
+		if repetitions < 2 || len(sID)%patternLength != 0 {
+			continue
+		}
+		if strings.Repeat(sID[:patternLength], repetitions) == sID {
+			return true
+		}
+	}
+	return false
+}
 
 func ParseInput(filepath string) []string {
 	content, _ := os.ReadFile(filepath)
@@ -33,7 +43,7 @@ func PartOne(input []string) int {
 			start, _ := strconv.Atoi(parts[0])
 			end, _ := strconv.Atoi(parts[1])
 			for id := start; id <= end; id++ {
-				if isInvalidID(id) {
+				if isInvalid(id, true) {
 					sum += id
 				}
 			}