[GitHub] [lucene] romseygeek commented on a diff in pull request #12286: toposort use iterator to avoid stackoverflow

["romseygeek (via GitHub)" <gi...@apache.org>]

romseygeek commented on code in PR #12286:
URL: https://github.com/apache/lucene/pull/12286#discussion_r1193625395


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lucene/core/src/java/org/apache/lucene/util/automaton/Operations.java:
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@@ -1303,24 +1307,49 @@ public static int[] topoSortStates(Automaton a) {
     return states;
   }
 
-  // TODO: not great that this is recursive... in theory a
-  // large automata could exceed java's stack so the maximum level of recursion is bounded to 1000
-  private static int topoSortStatesRecurse(
-      Automaton a, BitSet visited, int[] states, int upto, int state, int level) {
-    if (level > MAX_RECURSION_LEVEL) {
-      throw new IllegalArgumentException("input automaton is too large: " + level);
-    }
+  /**
+   * Performs a topological sort on the states of the given Automaton.
+   *
+   * @param a The automaton whose states are to be topologically sorted.
+   * @param states An int array which stores the states.
+   * @return the reversed topologically sorted array of state ids

Review Comment:
   minor nit: this should say 'returns the number of states in the final sorted list' I think?



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