Big O notation for triangular numbers?

Question

What\'s the correct big O notation for an algorithm that runs in triangular time? Here\'s an example:

func(x):
  for i in 0..x
    for j in 0..i
      do_som         


        

Answer 1

Yeah, O(n^2) is definitly correct. If I recall correctly, O is anyway always an upper bound, so O(n^3) should IMO also be correct, as would O(n^n) or whatever. However O(n^2) seems to be the most tight one that is easily deductable.