Coverage Summary for Class: DigGrid (day18p2)

 package day18p2
 
 import java.util.*
 import kotlin.math.absoluteValue
 import kotlin.math.max
 import kotlin.math.min
 
 fun String.lavaCapacityOriginal(): Long {
   val digPlan = toDigPlanOriginal()
   val digGrid = digPlan.dig()
   return digGrid.capacity()
 }
 
 fun String.lavaCapacityUpdated(): Long {
   val digPlan = toDigPlanUpdated()
   val digGrid = digPlan.dig()
   return digGrid.capacity()
 }
 
 fun String.toDigPlanOriginal(): DigPlan = DigPlan(
   lines().map { it.toStepOriginal() }.toList()
 )
 
 
 private val stepRegexOriginal = """([RLUD]) (\d+) .*""".toRegex()
 
 fun String.toStepOriginal(): Step =
   stepRegexOriginal.matchEntire(this)!!.destructured
     .let { (direction, distance) ->
       Step(
         direction = Direction.valueOf(direction),
         distance = distance.toInt()
       )
     }
 
 fun String.toDigPlanUpdated(): DigPlan = DigPlan(
   lines().map { it.toStepUpdated() }.toList()
 )
 
 
 private val stepRegexUpdated = """.*\(#(\w+)([0-3])\)""".toRegex()
 
 fun String.toStepUpdated(): Step =
   stepRegexUpdated.matchEntire(this)!!.destructured
     .let { (distanceHex, directionCode) ->
       Step(
         direction = when (directionCode) {
           "0" -> Direction.R
           "1" -> Direction.D
           "2" -> Direction.L
           else -> {
             require(directionCode == "3")
             Direction.U
           }
         },
         distance = distanceHex.toInt(16),
       )
     }
 
 data class DigPlan(val steps: List<Step>) {
   val length: Long = steps.sumOf { it.distance.toLong() }
   val lengthByDirection = steps.groupBy { it.direction }.mapValues { (_, steps) -> steps.sumOf { it.distance } }
   fun toText(): String = steps.joinToString("\n")
 
   fun isLoop(): Boolean =
     lengthByDirection[Direction.R] == lengthByDirection[Direction.L] &&
       lengthByDirection[Direction.U] == lengthByDirection[Direction.D]
 
   fun rows(): Indexes {
     var max = 0
     var current = 0
     var min = 0
     for (step in steps) {
       when (step.direction) {
         Direction.D -> {
           current += step.distance
           max = max.coerceAtLeast(current)
         }
 
         Direction.U -> {
           current -= step.distance
           min = min.coerceAtMost(current)
         }
 
         else -> continue
       }
     }
     return Indexes(max, min)
   }
 
   fun columns(): Indexes {
     var max = 0
     var current = 0
     var min = 0
     for (step in steps) {
       when (step.direction) {
         Direction.R -> {
           current += step.distance
           max = max.coerceAtLeast(current)
         }
 
         Direction.L -> {
           current -= step.distance
           min = min.coerceAtMost(current)
         }
 
         else -> continue
       }
     }
     return Indexes(max, min)
   }
 
   data class Indexes(val max: Int, val min: Int) {
     val total: Int = max - min + 1
   }
 
   fun dig(): DigGrid {
     val columnIndexes = columns()
     val rowIndexes = rows()
     val columns = TreeSet<BorderColumn>()
     val rows = TreeSet<BorderRow>()
     var currentCol = columnIndexes.min.absoluteValue
     var currentRow = rowIndexes.min.absoluteValue
     for (step in steps) {
       when (step.direction) {
         Direction.D -> {
           val col = BorderColumn(currentCol, currentRow, currentRow + step.distance)
           columns.add(col)
           currentRow = col.rowEnd
         }
 
         Direction.U -> {
           val col = BorderColumn(currentCol, currentRow - step.distance, currentRow)
           columns.add(col)
           currentRow = col.rowStart
         }
 
         Direction.L -> {
           val row = BorderRow(currentRow, currentCol - step.distance, currentCol)
           rows.add(row)
           currentCol = row.colStart
         }
 
         Direction.R -> {
           val row = BorderRow(currentRow, currentCol, currentCol + step.distance)
           rows.add(row)
           currentCol = row.colEnd
         }
       }
     }
 
     val finalColumns = TreeSet<BorderColumn>()
     for (col in columns) {
       val splitters =
         rows.asSequence().map { it.row }.distinct().filter { row -> col.rowStart < row && row < col.rowEnd }
           .toMutableList()
       var remaining = col
       while (splitters.isNotEmpty()) {
         val splitter = splitters.removeFirst()!!
         val (firstPart, secondPart) = remaining.split(splitter)
         finalColumns.add(firstPart)
         remaining = secondPart
       }
       finalColumns.add(remaining)
     }
 
     return DigGrid(columnIndexes.total, rowIndexes.total, finalColumns, rows)
   }
 }
 
 data class DigGrid(
   val numOfColumns: Int,
   val numOfRows: Int,
   val columns: TreeSet<BorderColumn>,
   val rows: TreeSet<BorderRow>
 ) {
   val length: Long =
     columns.sumOf { it.rowEnd.toLong() - it.rowStart } + rows.sumOf { it.colEnd.toLong() - it.colStart }
 
   override fun toString(): String = columns.joinToString("\n") + "\n" + rows.joinToString("\n")
   fun capacity(): Long {
 
     val columns = TreeSet(columns)
     val rowsByRowNum = rows.groupBy { it.row }
 
     var total = length
 
     while (columns.isNotEmpty()) {
       val first = columns.removeFirst()!!
       val second = columns.removeFirst()!!
       require(first.col < second.col)
       require(first.rowStart == second.rowStart)
       val commonEnd = min(first.rowEnd, second.rowEnd)
 
       val rowsInSameRow = rowsByRowNum.getValue(commonEnd)
       val gapStart = rowsInSameRow.firstOrNull { first.col in it.colStart..it.colEnd }?.colEnd ?: first.col
       val gapEnd = rowsInSameRow.firstOrNull { second.col in it.colStart..it.colEnd }?.colStart ?: second.col
       val totalGap = max(0, gapEnd - gapStart - 1)
       val borderGap = rowsInSameRow.sumOf { it.between(gapStart, gapEnd) }
       val gap = totalGap - borderGap
 
 
       total += gap
 
       val colDiff: Long = second.col - first.col - 1L
       val rowDiff: Long = commonEnd - first.rowStart - 1L
       val area: Long = colDiff * rowDiff
 
       total += area
     }
 
     return total
   }
 }
 
 data class BorderColumn(val col: Int, val rowStart: Int, val rowEnd: Int) : Comparable<BorderColumn> {
   override fun toString(): String = "$col, ($rowStart, $rowEnd)"
 
   override fun compareTo(other: BorderColumn): Int = compareValuesBy(this, other,
     { it.rowStart },
     { it.col }
   )
 
   fun split(splitter: Int): Pair<BorderColumn, BorderColumn> = copy(rowEnd = splitter) to copy(rowStart = splitter)
 }
 
 data class BorderRow(val row: Int, val colStart: Int, val colEnd: Int) : Comparable<BorderRow> {
   override fun toString(): String = "$row, ($colStart, $colEnd)"
 
   override fun compareTo(other: BorderRow): Int = compareValuesBy(this, other,
     { it.row },
     { it.colStart }
   )
 
   fun between(start: Int, end: Int): Int {
     if (colEnd <= start) return 0
     if (end <= colStart) return 0
     return min(end - 1, colEnd) - max(start + 1, colStart) + 1
   }
 }
 
 data class Step(val direction: Direction, val distance: Int) {
   override fun toString(): String = "$direction $distance"
 }
 
 enum class Direction {
   R,
   L,
   U,
   D;
 }