Sure, here are some clarifications:

O notation is a mathematical notation used to express upper bounds on the runtime or space complexity of algorithms. For example, O(log n) means that the time/space complexity grows logarithmically with the input size n. O(log^2 n) means the complexity grows quadratically with the logarithm of n. O(n) means linear complexity.

Generally speaking, VEB tree has better time complexity for insertion/deletion and range queries, and requires less space. However, fusion tree may be simpler to implement.
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