Coverage Summary for Class: History (day09p2)

 package day09p2
 
 fun List<Long>.predictPreviousValue(): Long {
   var result = first()
   var mult = -1
   var current = this
   while (!current.isAllZero()) {
     current = current.diffSeries()
     result += mult * current.first()
     mult *= -1
   }
   return result
 }
 
 fun List<Long>.predictNextValue(): Long {
   var result = last()
   var current = this
   while (!current.isAllZero()) {
     current = current.diffSeries()
     result += current.last()
   }
   return result
 }
 
 fun List<Long>.isAllZero(): Boolean = all { it == 0L }
 
 fun List<Long>.diffSeries(): List<Long> = windowed(2).map { it[1] - it[0] }
 
 fun String.toOASISReport(): OASISReport = OASISReport(lines().map { it.toHistory() })
 
 data class OASISReport(val entries: List<History>) {
   fun sumOfPredictedNextValues(): Long = entries.sumOf { it.predictNextValue() }
   fun sumOfPredictedPreviousValues(): Long = entries.sumOf { it.predictPreviousValue() }
 }
 
 fun String.toHistory(): History = History(
   """(-?\d+)""".toRegex().findAll(this).map { it.value.toLong() }.toList()
 )
 
 data class History(val entries: List<Long>) {
   fun predictNextValue(): Long = entries.predictNextValue()
   fun predictPreviousValue(): Long = entries.predictPreviousValue()
 }