diff --git a/days/day22.st b/days/day22.st
index 0500a30..2c1a90f 100644
--- a/days/day22.st
+++ b/days/day22.st
@@ -3,24 +3,48 @@ Object subclass: Monkey [
     history: h [history := h]
     lastValue [^history at: history size]
 
-    collectPricesInto: intoTbl
-    [ | ch table prices deltas chMod |
-      table := Dictionary new.
+    collectPricesInto: intoTbl seen: seenTbl
+    [ | ch prices deltas key newV prevSeen localBest |
       prices := history collect: [:it | it \\ 10].
       deltas := 2 to: history size collect: [
-                        :i | (prices at: i) - (prices at: i - 1) + 9].
-      ch := 0.
-      1 to: 4 do: [
-              :i | ch := 20 * ch + (deltas at: i)].
-      chMod := 20 raisedTo: 4.
+                    :i | (prices at: i) - (prices at: i - 1) + 9].
+      ch := 0. "past four deltas as a base-19 integer"
+      1 to: 4 do: [:i | ch := 19 * ch + (deltas at: i)].
+      "Accumulate the best value globally, (local variable as a
+       'compiler' optimisation)."
+      localBest := Monkey bestBananas.
       5 to: deltas size do: [
-          :i | ch := (20 * ch + (deltas at: i)) \\ chMod.
-          table at: ch ifAbsentPut: [prices at: i + 1]].
-      table keysAndValuesDo: [
-          :ch :v | intoTbl at: ch put: v + (intoTbl at: ch ifAbsent: [0])]]
+          :i | ch := (19 * ch + (deltas at: i)) \\ 130321.
+          "ch is theoretically in the range [0,19^4),
+           so add 1 to keep it in array range"
+          key := ch + 1.
+          (seenTbl at: key) == false ifTrue: [
+              "Store a linked list of seen values within the table,
+               to make resetting it easier."
+              seenTbl at: key put: prevSeen.
+              prevSeen := key.
+              newV := (prices at: i + 1) + (intoTbl at: key).
+              intoTbl at: key put: newV.
+              newV > localBest ifTrue: [localBest := newV].
+          ]].
+      Monkey bestBananas: localBest.
+      "Reset the seen table via the linked list."
+      [prevSeen notNil] whileTrue: [
+          | tmp | tmp := seenTbl at: prevSeen.
+          seenTbl at: prevSeen put: false.
+          prevSeen := tmp. ]]
 ]
 
 Monkey class extend [
+    | bestV |
+    bestBananas: v [bestV := v]
+    bestBananas [^bestV]
+
+    initialize [bestV := 0]
+
+    keyDigits [^19]
+    keyMax [^130321 "19 raisedTo: 4"]
+
     stepSecret: initial times: n
     [ | s hist | s := initial.
       hist := 1 to: n collect: [
@@ -31,12 +55,15 @@ Monkey class extend [
           s ].
       ^Monkey new history: {initial},hist ]
 ]
+Monkey initialize.
 
 AOC input: [ stdin toLines collect: [
                :it | Monkey stepSecret: it asNumber times: 2000] ];
     part1: [ :monkeys | (monkeys collect: [:it | it lastValue]) sum ];
-    part2: [ :monkeys | | buyMap | buyMap := Dictionary new.
-             monkeys do: [:it | it collectPricesInto: buyMap].
-             buyMap values maximum ];
+    part2: [ :monkeys | | buyMap seenMap |
+             buyMap := Array new: Monkey keyMax withAll: 0.
+             seenMap := Array new: Monkey keyMax withAll: false.
+             monkeys do: [:it | it collectPricesInto: buyMap seen: seenMap].
+             Monkey bestBananas ];
     result: [ :monkeys :part | part value: monkeys ];
     finish.