Big O - O(log(n)) code example

Question

Like the Big O notation \"O(1)\" can describe following code:

O(1):

    for (int i = 0; i < 10; i++) {
        // do stuff 
        a[i] = INT;
    }

O         


        

Answer 1

From definition, log(n) (I mean here log with base 2, but the base really doesn't matter), is the number of times, that you have to multiply 2 by itself to get n. So, O(log(n)) code example is:

i = 1
while(i < n)
    i = i * 2
    // maybe doing addition O(1) code

In real code examples, you can meet O(log(n)) in binary search, balanced binary search trees, many resursive algoritmhs, priority queues.