Merge pull request #411 from alreadydone/next

featurecat · Nov 3, 2018 · a066f38 · a066f38
2 parents 9257fd3 + 3f54f4e
commit a066f38
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diff --git a/src/main/java/featurecat/lizzie/rules/Board.java b/src/main/java/featurecat/lizzie/rules/Board.java
@@ -398,7 +398,7 @@ public void place(int x, int y, Stone color, boolean newBranch) {
               0);
 
       // don't make this coordinate if it is suicidal or violates superko
-      if (isSuicidal > 0 || history.violatesSuperko(newState)) return;
+      if (isSuicidal > 0 || history.violatesKoRule(newState)) return;
 
       // update leelaz with board position
       if (Lizzie.frame.isPlayingAgainstLeelaz

diff --git a/src/main/java/featurecat/lizzie/rules/BoardHistoryList.java b/src/main/java/featurecat/lizzie/rules/BoardHistoryList.java
@@ -185,6 +185,14 @@ public boolean violatesSuperko(BoardData data) {
     return false;
   }
 
+  public boolean violatesKoRule(BoardData data) {
+    // check if the current position is identical to the position two moves ago
+    return this.head
+        .previous()
+        .map(p -> p != null && data.zobrist.equals(p.getData().zobrist))
+        .orElse(false);
+  }
+
   /**
    * Returns the root node
    *