Question

I have written a simple algorithm to re-order the items in a list whenever the user drag and drop them. Also, if an item is deleted or a now one is added the list will be re-ordered. The algorithm contains three separated linear for loops (each one of them is O(n) ) and has two nested loops ( O(n^2) ). Is the total complexity O( n+ n +n + n^2) = O (3n+ n^2)?

How can I calculate the total big O ?

Thank you in advance

Answer 1

O(3n + n^2) is the same thing as O(n^2).

Big O notation only describes limiting behavior, and both functions have the same limiting behavior — doubling n quadruples them. (As n goes to infinity, the 3n component becomes smaller and smaller relative to the n^2 component. At the limit, it completely dominates it.)