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day21/src/day21.cs

@@ -66,6 +66,7 @@ long OccupiedCountSmart(List<List<long>> maze, int steps)
  counts.Add(current.Count);
  }
  // Then extrapolate the quadratic sequence
+ // (degree 2 case of polynomial extrapolation using finite differences)
  var diffs = Differences(counts); // Should be an arithmetic progression
  var diffs2 = Differences(diffs); // Should be a list of equal values
  for (int i = 0; i < fullLengthSteps; i++)