88 lines
2.1 KiB
Go
88 lines
2.1 KiB
Go
package daytwo
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import (
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"os"
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"strconv"
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"strings"
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"advent-of-code/internal/registry"
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)
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func init() {
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registry.Register("2025D2", ParseInput, PartOne, PartTwo)
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}
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func ParseInput(filepath string) []string {
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content, _ := os.ReadFile(filepath)
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return strings.Split(strings.TrimSpace(string(content)), "\n")
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}
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func PartOne(input []string) int {
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sum := 0
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for _, line := range input {
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for newRange := range strings.SplitSeq(line, ",") {
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parts := strings.Split(newRange, "-")
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start, _ := strconv.Atoi(parts[0])
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end, _ := strconv.Atoi(parts[1])
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for id := start; id <= end; id++ {
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sID := strconv.Itoa(id)
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if len(sID)%2 == 0 {
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half := len(sID) / 2
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if sID[:half] == sID[half:] {
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sum += id
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}
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}
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}
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}
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}
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return sum
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}
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func PartTwo(input []string) int {
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totalSum := 0
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for _, line := range input {
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for rangeSpec := range strings.SplitSeq(line, ",") {
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rangeStartStr, rangeEndStr, _ := strings.Cut(rangeSpec, "-")
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rangeStart, _ := strconv.Atoi(rangeStartStr)
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rangeEnd, _ := strconv.Atoi(rangeEndStr)
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seenNumbers := make(map[int]bool)
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maxDigits := len(rangeEndStr)
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var generatePatterns func(string, int, int)
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generatePatterns = func(currentPattern string, targetPatternLength, currentDepth int) {
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if currentDepth == targetPatternLength {
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repeated := currentPattern + currentPattern
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for len(repeated) <= maxDigits {
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number, err := strconv.Atoi(repeated)
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if err != nil || number > rangeEnd {
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break
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}
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if number >= rangeStart && !seenNumbers[number] {
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totalSum += number
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seenNumbers[number] = true
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}
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repeated += currentPattern
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}
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return
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}
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minDigit := 0
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if currentDepth == 0 {
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minDigit = 1
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}
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for digit := minDigit; digit <= 9; digit++ {
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extendedPattern := currentPattern + strconv.Itoa(digit)
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generatePatterns(extendedPattern, targetPatternLength, currentDepth+1)
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}
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}
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for patternLength := 1; patternLength <= maxDigits/2; patternLength++ {
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generatePatterns("", patternLength, 0)
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}
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}
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}
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return totalSum
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}
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