130 lines
4.2 KiB
Scala
130 lines
4.2 KiB
Scala
object UPC {
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private val SEVEN = 7
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private val LEFT_DIGITS = Map(
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" ## #" -> 0,
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" ## #" -> 1,
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" # ##" -> 2,
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" #### #" -> 3,
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" # ##" -> 4,
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" ## #" -> 5,
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" # ####" -> 6,
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" ### ##" -> 7,
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" ## ###" -> 8,
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" # ##" -> 9
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)
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private val RIGHT_DIGITS = LEFT_DIGITS.map { case (key, value) =>
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key.replace(' ', 's').replace('#', ' ').replace('s', '#') -> value
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}
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private val END_SENTINEL = "# #"
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private val MID_SENTINEL = " # # "
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private def decode(candidate: String): (Boolean, List[Int]) = {
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var pos = 0
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val output = scala.collection.mutable.ListBuffer[Int]()
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// Check start sentinel
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if (candidate.length < pos + END_SENTINEL.length ||
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candidate.substring(pos, pos + END_SENTINEL.length) != END_SENTINEL) {
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return (false, output.toList)
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}
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pos += END_SENTINEL.length
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// Decode left side digits
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for (_ <- 1 until SEVEN) {
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if (candidate.length < pos + SEVEN) {
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return (false, output.toList)
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}
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val part = candidate.substring(pos, pos + SEVEN)
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pos += SEVEN
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LEFT_DIGITS.get(part) match {
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case Some(digit) => output += digit
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case None => return (false, output.toList)
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}
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}
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// Check middle sentinel
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if (candidate.length < pos + MID_SENTINEL.length ||
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candidate.substring(pos, pos + MID_SENTINEL.length) != MID_SENTINEL) {
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return (false, output.toList)
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}
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pos += MID_SENTINEL.length
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// Decode right side digits
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for (_ <- 1 until SEVEN) {
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if (candidate.length < pos + SEVEN) {
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return (false, output.toList)
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}
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val part = candidate.substring(pos, pos + SEVEN)
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pos += SEVEN
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RIGHT_DIGITS.get(part) match {
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case Some(digit) => output += digit
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case None => return (false, output.toList)
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}
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}
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// Check end sentinel
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if (candidate.length < pos + END_SENTINEL.length ||
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candidate.substring(pos, pos + END_SENTINEL.length) != END_SENTINEL) {
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return (false, output.toList)
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}
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// Calculate checksum
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val sum = output.zipWithIndex.map { case (digit, index) =>
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if (index % 2 == 0) 3 * digit else digit
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}.sum
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(sum % 10 == 0, output.toList)
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}
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private def printList(list: List[Int]): Unit = {
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print("[")
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print(list.mkString(", "))
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print("]")
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}
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private def decodeUPC(input: String): Unit = {
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val candidate = input.trim
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val (isValid, digits) = decode(candidate)
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if (isValid) {
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printList(digits)
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println()
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} else {
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// Try upside down
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val reversed = candidate.reverse
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val (isValidReversed, digitsReversed) = decode(reversed)
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if (isValidReversed) {
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printList(digitsReversed)
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println(" Upside down")
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} else if (digitsReversed.length == 12) {
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println("Invalid checksum")
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} else {
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println("Invalid digit(s)")
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}
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}
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}
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def main(args: Array[String]): Unit = {
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val barcodes = List(
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" # # # ## # ## # ## ### ## ### ## #### # # # ## ## # # ## ## ### # ## ## ### # # # ",
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" # # # ## ## # #### # # ## # ## # ## # # # ### # ### ## ## ### # # ### ### # # # ",
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" # # # # # ### # # # # # # # # # # ## # ## # ## # ## # # #### ### ## # # ",
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" # # ## ## ## ## # # # # ### # ## ## # # # ## ## # ### ## ## # # #### ## # # # ",
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" # # ### ## # ## ## ### ## # ## # # ## # # ### # ## ## # # ### # ## ## # # # ",
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" # # # # ## ## # # # # ## ## # # # # # #### # ## # #### #### # # ## # #### # # ",
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" # # # ## ## # # ## ## # ### ## ## # # # # # # # # ### # # ### # # # # # ",
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" # # # # ## ## # # ## ## ### # # # # # ### ## ## ### ## ### ### ## # ## ### ## # # ",
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" # # ### ## ## # # #### # ## # #### # #### # # # # # ### # # ### # # # ### # # # ",
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" # # # #### ## # #### # # ## ## ### #### # # # # ### # ### ### # # ### # # # ### # # "
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)
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barcodes.foreach(decodeUPC)
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}
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}
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