Further cleanup, solvers are now separate implementations of CrossSolver

src/main/kotlin/be/nielandt/CrossSolver.kt

@@ -3,6 +3,30 @@ package be.nielandt
 import java.time.Duration
 import java.time.Instant
 
+open abstract class CrossSolver {
+    /**
+     * Solve all crosses, look for a minimal set of moves for each color's cross.
+     */
+    abstract fun solveCrosses(edgeModel: EdgeModel): Map<Int, List<Move>>
+
+    fun solveCrossesTimed(edgeModel: EdgeModel): Map<Int, List<Move>> {
+        val now = Instant.now()
+        val solveCrosses = solveCrosses(edgeModel)
+        val between = Duration.between(now, Instant.now())
+        println("Solving crosses took ${between.seconds}s")
+        return solveCrosses
+    }
+
+    companion object {
+        fun printResults(results: Map<Int, List<Move>>) {
+            println("results: ")
+            results.forEach { color, moveList ->
+                println("> color ${colorLetter(color)}, moves $moveList")
+            }
+        }
+    }
+}
+
 /**
  * Let's look for symmetries.
  */
@@ -37,241 +61,26 @@ fun main(args: Array<String>) {
 //    }
 
 
-    // make a beginning model, then start doing crazy shit
+    // do a fixed scramble for testing purposes
+    val fixedMoves = Move.parse("L L_ R R2")
+    println("fixedMoves = ${fixedMoves}")
+
+
+    // scramble random
     val moves = Move.random(20)
     println("Scramble: $moves")
     val scrambledModel = EdgeModel(moves)
     println(scrambledModel)
 
-//    doAllCrossMoveCounts(scrambledModel)
+    val baseSolve = CrossSolverBase().solveCrossesTimed(scrambledModel)
-//    val allCrossMoveCount = allCrossMoveCount(scrambledModel)
+    CrossSolver.printResults(baseSolve)
-//    allCrossMoveCount.forEach { color, moves ->
+
-//        println("cross for color: ${color} in ${moves.size}: ${moves.joinToString(" ")}")
+    val upgradedSolve = CrossSolverUpgraded().solveCrossesTimed(scrambledModel)
+    CrossSolver.printResults(upgradedSolve)
+
+//    val allCrossMoveCountUpgradedSkip = allCrossMoveCountUpgradedSkip(scrambledModel)
+//    allCrossMoveCountUpgradedSkip.forEach { color, moves ->
+//        println("skip upgrade cross for color: ${color} in ${moves.size}: ${moves.joinToString(" ")}")
 //    }
-    val allCrossMoveCountUpgraded = allCrossMoveCountUpgraded(scrambledModel)
-    allCrossMoveCountUpgraded.forEach { color, moves ->
-        println("upgrade cross for color: ${color} in ${moves.size}: ${moves.joinToString(" ")}")
-    }
-    val allCrossMoveCountUpgradedSkip = allCrossMoveCountUpgradedSkip(scrambledModel)
-    allCrossMoveCountUpgradedSkip.forEach { color, moves ->
-        println("skip upgrade cross for color: ${color} in ${moves.size}: ${moves.joinToString(" ")}")
-    }
 }
 
-/**
- * Do the color solves separately. Not very efficient, this rehashes a lot of things.
- */
-fun doAllCrossMoveCounts(edgeModel: EdgeModel) {
-    for (c: Color in Color.values()) {
-        val crossMoveCount = crossMoveCount(edgeModel, c)
-        println("${c} in ${crossMoveCount?.size}: ${crossMoveCount?.joinToString()}")
-    }
-}
-
-/**
- * For a single color, go 8 deep and try and find the minimal amount of moves to solve that cross.
- */
-fun crossMoveCount(edgeModel: EdgeModel, color: Color): List<Move>? {
-    val moveCounts = Array<List<Move>?>(6) { null }
-
-    for (moveCount in 1..8) {
-        // build a counter of moveCount big
-        val counter = Counter(moveCount, Move.values().size)
-
-        // count up, each state of the counter corresponds to a combination of moves
-        do {
-            // what is the move combination we're looking at?
-            val moves = Move.combo(counter)
-            // execute the moves
-            val afterMoves = edgeModel.doMoves(moves)
-            val crossSolved = afterMoves.crossSolved(color)
-            if (crossSolved) {
-                return@crossMoveCount moves
-            }
-
-        } while (counter.increase())
-    }
-    return null
-}
-
-/**
- * Solve the minimal cross for all colors. Try to upgrade the method... Can we cache the 'previous results'?
- */
-fun allCrossMoveCountUpgradedSkip(edgeModel: EdgeModel): Map<Color, List<Move>> {
-    val start = Instant.now()
-    val moveCounts = mutableMapOf<Color, List<Move>>()
-
-    for (moveCount in 1..8) {
-        println("all cross move count upgrade doing $moveCount")
-        // build a counter of moveCount big
-        val counter = Counter(moveCount, Move.values().size)
-        val edgeModelFactory = EdgeModelFactory(edgeModel, counter, true)
-
-        println("moveCounts = ${moveCounts}")
-
-        while (edgeModelFactory.hasNext()) {
-            // get the next model, using the internal counter which simply iterates over possible combinations of moves
-            val next = edgeModelFactory.getNext()
-
-            // check crosses that have not been found yet
-            Color.values().forEach { color ->
-                if (!moveCounts.containsKey(color)) {
-                    val crossSolved = next.crossSolved(color)
-                    if (crossSolved) {
-                        // what is the move combination we're looking at?
-                        val moves = Move.combo(counter)
-                        moveCounts[color] = moves
-                    }
-                }
-            }
-            // break if we have found hem all
-            if (moveCounts.keys.size == Color.values().size) {
-                println("Execution time: ${Duration.between(start, Instant.now()).toMillis() / 1000}s")
-//                println("counter.skipInvalidCount = ${counter.skipInvalidCount}")
-                return moveCounts
-            }
-        }
-    }
-    println("Execution time: ${Duration.between(start, Instant.now()).toMillis() / 1000}s")
-    return moveCounts
-}
-/**
- * Solve the minimal cross for all colors. Try to upgrade the method... Can we cache the 'previous results'?
- */
-fun allCrossMoveCountUpgraded(edgeModel: EdgeModel): Map<Color, List<Move>> {
-    val start = Instant.now()
-    val moveCounts = mutableMapOf<Color, List<Move>>()
-
-    for (moveCount in 1..8) {
-        println("all cross move count upgrade doing $moveCount")
-        // build a counter of moveCount big
-        val counter = Counter(moveCount, Move.values().size)
-        val edgeModelFactory = EdgeModelFactory(edgeModel, counter)
-
-        while (edgeModelFactory.hasNext()) {
-            // get the next model, using the internal counter which simply iterates over possible combinations of moves
-            val next = edgeModelFactory.getNext()
-
-            // check crosses that have not been found yet
-            Color.values().forEach { color ->
-                if (!moveCounts.containsKey(color)) {
-                    val crossSolved = next.crossSolved(color)
-                    if (crossSolved) {
-                        // what is the move combination we're looking at?
-                        val moves = Move.combo(counter)
-                        moveCounts[color] = moves
-                    }
-                }
-            }
-            // break if we have found hem all
-            if (moveCounts.keys.size == Color.values().size) {
-                println("Execution time: ${Duration.between(start, Instant.now()).toMillis() / 1000}s")
-                return moveCounts
-            }
-        }
-    }
-    println("Execution time: ${Duration.between(start, Instant.now()).toMillis() / 1000}s")
-    return moveCounts
-}
-
-/**
- * This thing helps us to create edgemodels using a counter. The advantage is that the edgemodel doesn't need to be calculated
- * completely from scratch: previous states are kept, so if, e.g., the third digit changes in the counter (of length 5),
- * the previous state that was calculated using the first two states is used to perform move 3,4,5 on.
- *
- * This is probably equivalent to 8 nested for loops, you'd be able to keep track of temporary solutions there too....
- */
-class EdgeModelFactory(val original: EdgeModel, val counter: Counter, val skip: Boolean = false) {
-    // keep a modified version of the edgemodel for each digit in the counter, from left to right
-    private val history: MutableList<EdgeModel> = mutableListOf()
-
-    // we always have one in the beginning: the initial state of the counter
-    private var hasNext: Boolean = true
-
-    init {
-        // init the history
-        this.history.add(original.doMove(Move.values()[counter.digit(0)]))
-        for (i in 1 until counter.size()) {
-            this.history.add(this.history.last().doMove(Move.values()[counter.digit(i)]))
-        }
-    }
-
-    fun hasNext(): Boolean {
-        return hasNext
-    }
-
-    fun getNext(): EdgeModel {
-        // the counter was increased, hooray
-        val lastOverflowIndex = counter.getLastModifiedIndex()
-        // we only need to redo everything starting from the lastoverflowindex
-        // these are our moves, but we can salvage everything up to lastoverflowindex
-        val moves = Move.combo(counter)
-        // we have a history to work with... only redo what's necessary
-        for (i in counter.getLastModifiedIndex() until counter.size()) {
-            var start: EdgeModel?
-            start = if (i == 0)
-                original
-            else
-                history[i - 1]
-            history[i] = start.doMove(Move.values()[counter.digit(i)])
-        }
-        // increase the counter for next time
-        if(!skip) {
-            if (!counter.increase()) {
-                this.hasNext = false
-            }
-        } else {
-            if (!counter.increaseAndSkipInvalid()) {
-                this.hasNext = false
-            }
-        }
-        // the last item in the history is now the edgemodel we need to test...
-        return history.last()
-    }
-}
-
-/**
- * Solve the minimal cross for all colors.
- */
-fun allCrossMoveCount(edgeModel: EdgeModel): Map<Color, List<Move>> {
-    val start = Instant.now()
-    val moveCounts = mutableMapOf<Color, List<Move>>()
-
-    for (moveCount in 1..8) {
-        // build a counter of moveCount big
-        println("allCrossMoveCount basic doing $moveCount")
-        val counter = Counter(moveCount, Move.values().size)
-
-        // count up, each state of the counter corresponds to a combination of moves
-        do {
-            // what is the move combination we're looking at?
-            val moves = Move.combo(counter)
-            // execute the moves
-            val afterMoves = edgeModel.doMoves(moves)
-            // check crosses that have not been found yet
-            Color.values().forEach { color ->
-                if (!moveCounts.containsKey(color)) {
-                    val crossSolved = afterMoves.crossSolved(color)
-                    if (crossSolved) {
-                        moveCounts[color] = moves
-                    }
-                }
-            }
-
-            if (moveCounts.keys.size == Color.values().size) {
-                println("Execution time: ${Duration.between(start, Instant.now()).toMillis() / 1000}s")
-                return@allCrossMoveCount moveCounts
-            }
-
-        } while (counter.increase())
-    }
-    println("Execution time: ${Duration.between(start, Instant.now()).toMillis() / 1000}s")
-    return moveCounts
-}
-
-/**
- * Convert the color into a single digit for print purposes.
- */
-fun l(c: Color): String {
-    return c.name.first().toString()
-}

src/main/kotlin/be/nielandt/CrossSolverBase.kt

@@ -0,0 +1,40 @@
+package be.nielandt
+
+class CrossSolverBase : CrossSolver() {
+    /**
+     * Solve the minimal cross for all colors.
+     */
+    override fun solveCrosses(edgeModel: EdgeModel): Map<Int, List<Move>> {
+        val moveCounts = mutableMapOf<Int, List<Move>>()
+
+        for (moveCount in 1..8) {
+            // build a counter of moveCount big
+            println("allCrossMoveCount basic doing $moveCount")
+            val counter = Counter(moveCount, Move.values().size)
+
+            // count up, each state of the counter corresponds to a combination of moves
+            do {
+                // what is the move combination we're looking at?
+                val moves = Move.combo(counter)
+                // execute the moves
+                val afterMoves = edgeModel.doMoves(moves)
+                // check crosses that have not been found yet
+                (0..5).forEach { color ->
+                    if (!moveCounts.containsKey(color)) {
+                        val crossSolved = afterMoves.crossSolved(color)
+                        if (crossSolved) {
+                            moveCounts[color] = moves
+                        }
+                    }
+                }
+
+                if (moveCounts.keys.size == 6) {
+                    return@solveCrosses moveCounts
+                }
+
+            } while (counter.increase())
+        }
+        return moveCounts
+    }
+
+}

src/main/kotlin/be/nielandt/CrossSolverUpgraded.kt

@@ -0,0 +1,43 @@
+package be.nielandt
+
+import java.time.Instant
+
+/**
+ * This solver avoids redoing edgemodel manipulations. Should be equivalent to X nested for loops.
+ */
+class CrossSolverUpgraded : CrossSolver() {
+
+    override fun solveCrosses(edgeModel: EdgeModel): Map<Int, List<Move>> {
+        val start = Instant.now()
+        val moveCounts = mutableMapOf<Int, List<Move>>()
+
+        for (moveCount in 1..8) {
+            println("all cross move count upgrade doing $moveCount")
+            // build a counter of moveCount big
+            val counter = Counter(moveCount, Move.values().size)
+            val edgeModelFactory = EdgeModelFactory(edgeModel, counter)
+
+            while (edgeModelFactory.hasNext()) {
+                // get the next model, using the internal counter which simply iterates over possible combinations of moves
+                val next = edgeModelFactory.getNext()
+
+                // check crosses that have not been found yet
+                (0..5).forEach { color ->
+                    if (!moveCounts.containsKey(color)) {
+                        val crossSolved = next.crossSolved(color)
+                        if (crossSolved) {
+                            // what is the move combination we're looking at?
+                            val moves = Move.combo(counter)
+                            moveCounts[color] = moves
+                        }
+                    }
+                }
+                // break if we have found hem all
+                if (moveCounts.keys.size == 6) {
+                    return moveCounts
+                }
+            }
+        }
+        return moveCounts
+    }
+}

src/main/kotlin/be/nielandt/CrossSolverUpgradedSkip.kt

@@ -0,0 +1,45 @@
+package be.nielandt
+
+/**
+ * This solver avoids redoing edgemodel manipulations. Should be equivalent to X nested for loops.
+ */
+class CrossSolverUpgradedSkip : CrossSolver() {
+
+    override fun solveCrosses(edgeModel: EdgeModel): Map<Int, List<Move>> {
+        val moveCounts = mutableMapOf<Int, List<Move>>()
+
+        for (moveCount in 1..8) {
+            println("all cross move count upgrade doing $moveCount")
+            // build a counter of moveCount big
+            val counter = Counter(moveCount, Move.values().size)
+            // TODO skip the counter
+            val edgeModelFactory = EdgeModelFactory(edgeModel, counter)
+
+            println("moveCounts = ${moveCounts}")
+
+            while (edgeModelFactory.hasNext()) {
+                // get the next model, using the internal counter which simply iterates over possible combinations of moves
+                val next = edgeModelFactory.getNext()
+
+                // check crosses that have not been found yet
+                (0..5).forEach { color ->
+                    if (!moveCounts.containsKey(color)) {
+                        val crossSolved = next.crossSolved(color)
+                        if (crossSolved) {
+                            // what is the move combination we're looking at?
+                            val moves = Move.combo(counter)
+                            moveCounts[color] = moves
+                        }
+                    }
+                }
+                // break if we have found hem all
+                if (moveCounts.keys.size == 6) {
+//                println("counter.skipInvalidCount = ${counter.skipInvalidCount}")
+                    return moveCounts
+                }
+            }
+        }
+        return moveCounts
+
+    }
+}

src/main/kotlin/be/nielandt/EdgeModel.kt

@@ -26,7 +26,7 @@ package be.nielandt
 
 class EdgeModel {
 
-    val model: Array<Color>
+    val model: Array<Int>
 
     private val F = intArrayOf(13, 18, 7, 20, 3, 0, 1, 2)
     private val B = intArrayOf(8, 9, 10, 11, 16, 15, 22, 5)
@@ -46,12 +46,12 @@ class EdgeModel {
         }
 
         model = arrayOf(
-                Color.GREEN, Color.GREEN, Color.GREEN, Color.GREEN,
+                GREEN, GREEN, GREEN, GREEN,
-                Color.RED, Color.RED, Color.RED, Color.RED,
+                RED, RED, RED, RED,
-                Color.BLUE, Color.BLUE, Color.BLUE, Color.BLUE,
+                BLUE, BLUE, BLUE, BLUE,
-                Color.ORANGE, Color.ORANGE, Color.ORANGE, Color.ORANGE,
+                ORANGE, ORANGE, ORANGE, ORANGE,
-                Color.WHITE, Color.WHITE, Color.WHITE, Color.WHITE,
+                WHITE, WHITE, WHITE, WHITE,
-                Color.YELLOW, Color.YELLOW, Color.YELLOW, Color.YELLOW
+                YELLOW, YELLOW, YELLOW, YELLOW
         )
     }
 
@@ -61,7 +61,7 @@ class EdgeModel {
         this.model = doMoves.model
     }
 
-    constructor(model: Array<Color>) {
+    constructor(model: Array<Int>) {
         this.model = model
     }
 
@@ -154,17 +154,17 @@ class EdgeModel {
     override fun toString(): String {
         val trimMargin = """
         |        ---------
-        |        |   ${l(model[16])}   |
+        |        |   ${colorLetter(model[16])}   |
-        |        | ${l(model[19])} W ${l(model[17])} |
+        |        | ${colorLetter(model[19])} W ${colorLetter(model[17])} |
-        |        |   ${l(model[18])}   |
+        |        |   ${colorLetter(model[18])}   |
         |---------------------------------
-        ||   ${l(model[12])}   |   ${l(model[0])}   |   ${l(model[4])}   |   ${l(model[8])}   |
+        ||   ${colorLetter(model[12])}   |   ${colorLetter(model[0])}   |   ${colorLetter(model[4])}   |   ${colorLetter(model[8])}   |
-        || ${l(model[15])} O ${l(model[13])} | ${l(model[3])} G ${l(model[1])} | ${l(model[7])} R ${l(model[5])} | ${l(model[11])} B ${l(model[9])} |
+        || ${colorLetter(model[15])} O ${colorLetter(model[13])} | ${colorLetter(model[3])} G ${colorLetter(model[1])} | ${colorLetter(model[7])} R ${colorLetter(model[5])} | ${colorLetter(model[11])} B ${colorLetter(model[9])} |
-        ||   ${l(model[14])}   |   ${l(model[2])}   |   ${l(model[6])}   |   ${l(model[10])}   |
+        ||   ${colorLetter(model[14])}   |   ${colorLetter(model[2])}   |   ${colorLetter(model[6])}   |   ${colorLetter(model[10])}   |
         |---------------------------------
-        |        |   ${l(model[20])}   |
+        |        |   ${colorLetter(model[20])}   |
-        |        | ${l(model[23])} Y ${l(model[21])} |
+        |        | ${colorLetter(model[23])} Y ${colorLetter(model[21])} |
-        |        |   ${l(model[22])}   |
+        |        |   ${colorLetter(model[22])}   |
         |        ---------
         """.trimMargin()
         return trimMargin
@@ -182,31 +182,34 @@ class EdgeModel {
         return this.doMoves(f.toList())
     }
 
-    fun crossSolved(color: Color): Boolean {
+    fun crossSolved(color: Int): Boolean {
         return when (color) {
-            Color.WHITE -> {
+            WHITE -> {
-                model[WB] == Color.WHITE && model[WG] == Color.WHITE && model[WO] == Color.WHITE && model[WR] == Color.WHITE &&
+                model[WB] == WHITE && model[WG] == WHITE && model[WO] == WHITE && model[WR] == WHITE &&
-                        model[BW] == Color.BLUE && model[GW] == Color.GREEN && model[OW] == Color.ORANGE && model[RW] == Color.RED
+                        model[BW] == BLUE && model[GW] == GREEN && model[OW] == ORANGE && model[RW] == RED
             }
-            Color.YELLOW -> {
+            YELLOW -> {
-                model[YB] == Color.YELLOW && model[YG] == Color.YELLOW && model[YO] == Color.YELLOW && model[YR] == Color.YELLOW &&
+                model[YB] == YELLOW && model[YG] == YELLOW && model[YO] == YELLOW && model[YR] == YELLOW &&
-                        model[BY] == Color.BLUE && model[GY] == Color.GREEN && model[OY] == Color.ORANGE && model[RY] == Color.RED
+                        model[BY] == BLUE && model[GY] == GREEN && model[OY] == ORANGE && model[RY] == RED
             }
-            Color.RED -> {
+            RED -> {
-                model[RW] == Color.RED && model[RG] == Color.RED && model[RY] == Color.RED && model[RB] == Color.RED &&
+                model[RW] == RED && model[RG] == RED && model[RY] == RED && model[RB] == RED &&
-                        model[WR] == Color.WHITE && model[GR] == Color.GREEN && model[YR] == Color.YELLOW && model[BR] == Color.BLUE
+                        model[WR] == WHITE && model[GR] == GREEN && model[YR] == YELLOW && model[BR] == BLUE
             }
-            Color.BLUE -> {
+            BLUE -> {
-                model[BW] == Color.BLUE && model[BR] == Color.BLUE && model[BY] == Color.BLUE && model[BO] == Color.BLUE &&
+                model[BW] == BLUE && model[BR] == BLUE && model[BY] == BLUE && model[BO] == BLUE &&
-                        model[WB] == Color.WHITE && model[RB] == Color.RED && model[YB] == Color.YELLOW && model[OB] == Color.ORANGE
+                        model[WB] == WHITE && model[RB] == RED && model[YB] == YELLOW && model[OB] == ORANGE
             }
-            Color.GREEN -> {
+            GREEN -> {
-                model[GW] == Color.GREEN && model[GO] == Color.GREEN && model[GY] == Color.GREEN && model[GR] == Color.GREEN &&
+                model[GW] == GREEN && model[GO] == GREEN && model[GY] == GREEN && model[GR] == GREEN &&
-                        model[WG] == Color.WHITE && model[OG] == Color.ORANGE && model[YG] == Color.YELLOW && model[RG] == Color.RED
+                        model[WG] == WHITE && model[OG] == ORANGE && model[YG] == YELLOW && model[RG] == RED
             }
-            Color.ORANGE -> {
+            ORANGE -> {
-                model[OW] == Color.ORANGE && model[OB] == Color.ORANGE && model[OY] == Color.ORANGE && model[OG] == Color.ORANGE &&
+                model[OW] == ORANGE && model[OB] == ORANGE && model[OY] == ORANGE && model[OG] == ORANGE &&
-                        model[WO] == Color.WHITE && model[BO] == Color.BLUE && model[YO] == Color.YELLOW && model[GO] == Color.GREEN
+                        model[WO] == WHITE && model[BO] == BLUE && model[YO] == YELLOW && model[GO] == GREEN
+            }
+            else -> {
+                throw RuntimeException()
             }
         }
     }

src/main/kotlin/be/nielandt/EdgeModelConstants.kt

@@ -37,8 +37,25 @@ const val OY = 14
 /**
  * Six colors
  */
-enum class Color(index: Int) {
+const val WHITE = 0
-    WHITE(0), YELLOW(1), ORANGE(2), RED(3), GREEN(4), BLUE(5)
+const val YELLOW = 1
+const val ORANGE = 2
+const val RED = 3
+const val GREEN = 4
+const val BLUE = 5
+
+
+/**
+ * Convert the color into a single digit for print purposes.
+ */
+fun colorLetter(c: Int): String {
+    return when (c) {
+        WHITE -> "W"
+        YELLOW -> "Y"
+        RED -> "R"
+        BLUE -> "B"
+        GREEN -> "G"
+        ORANGE -> "O"
+        else -> "?"
+    }
 }
-
-

src/main/kotlin/be/nielandt/EdgeModelFactory.kt

@@ -0,0 +1,50 @@
+package be.nielandt
+
+/**
+ * This thing helps us to create edgemodels using a counter. The advantage is that the edgemodel doesn't need to be calculated
+ * completely from scratch: previous states are kept, so if, e.g., the third digit changes in the counter (of length 5),
+ * the previous state that was calculated using the first two states is used to perform move 3,4,5 on.
+ *
+ * This is probably equivalent to 8 nested for loops, you'd be able to keep track of temporary solutions there too....
+ */
+class EdgeModelFactory(val original: EdgeModel, val counter: Counter) {
+    // keep a modified version of the edgemodel for each digit in the counter, from left to right
+    private val history: MutableList<EdgeModel> = mutableListOf()
+
+    // we always have one in the beginning: the initial state of the counter
+    private var hasNext: Boolean = true
+
+    init {
+        // init the history
+        this.history.add(original.doMove(Move.values()[counter.digit(0)]))
+        for (i in 1 until counter.size()) {
+            this.history.add(this.history.last().doMove(Move.values()[counter.digit(i)]))
+        }
+    }
+
+    fun hasNext(): Boolean {
+        return hasNext
+    }
+
+    fun getNext(): EdgeModel {
+        // the counter was increased, hooray
+        val lastOverflowIndex = counter.getLastModifiedIndex()
+        // we only need to redo everything starting from the lastoverflowindex
+        // these are our moves, but we can salvage everything up to lastoverflowindex
+        val moves = Move.combo(counter)
+        // we have a history to work with... only redo what's necessary
+        for (i in counter.getLastModifiedIndex() until counter.size()) {
+            var start: EdgeModel = if (i == 0)
+                original
+            else
+                history[i - 1]
+            history[i] = start.doMove(Move.values()[counter.digit(i)])
+        }
+        // increase the counter for next time
+        if (!counter.increase()) {
+            this.hasNext = false
+        }
+        // the last item in the history is now the edgemodel we need to test...
+        return history.last()
+    }
+}

src/main/kotlin/be/nielandt/Move.kt

@@ -40,6 +40,19 @@ enum class Move {
             }
             return res
         }
+
+        /**
+         * Parse a set of moves, separated by spaces, using the Move.enum names.
+         */
+        fun parse(s: String): List<Move> {
+            val result = mutableListOf<Move>()
+            s.split(" ", ",", ";").forEach {
+                if (it.isNotEmpty()) {
+                    result.add(Move.valueOf(it))
+                }
+            }
+            return result
+        }
     }
 
     /**

src/test/kotlin/be/nielandt/EdgeModelTest.kt

@@ -1,6 +1,6 @@
 package be.nielandt
 
-import org.junit.Assert.*
+import org.junit.Assert.assertEquals
 import org.junit.Test
 
 class EdgeModelTest {
@@ -10,7 +10,7 @@ class EdgeModelTest {
         // try each move
         Move.values().forEach { move ->
             val doMove = EdgeModel().doMove(move)
-            val count = Color.values().map { color ->
+            val count = (0..5).map { color ->
                 val crossSolved = doMove.crossSolved(color)
                 crossSolved
             }.count { it }
@@ -18,14 +18,4 @@ class EdgeModelTest {
         }
     }
 
-    @Test
-    fun findAtLeastOneCombo() {
-        val white = Color.WHITE
-        val doMoves = EdgeModel().doMoves(Move.random(20))
-        val crossMoveCount = crossMoveCount(doMoves, Color.WHITE)
-        assertNotNull(crossMoveCount)
-        assertTrue(crossMoveCount!!.size<9)
-        println(doMoves)
-        println("crossMoveCount = $crossMoveCount")
-    }
 }