Order-of-Magnitude Analysis
If Alg A requires time proportional to f(N), Alg A is said to be order f(N), which is denoted by O(f(N));
f(N) is called the algorithm’s growth-rate function.
The notation uses the upper-case O to denote order, it is called the Big O notation.
If a problem size of N requires time that is directly proportional to N, the problem is O(N), if it is , then it is O( ), and so on.