Which of the following growth-rate functions would correspond to the shortest running time?

linear

logarithmic

constant

factorial

The answer is: constant.

Explanation:

The Big-Oh analysis informs what is the perform of an algorithm based on the input size (N). Having this in mind you have:

O (N) linear. O (log N) logarithmic. O (1) constant. O (n!) factorial.

The shortest running time is the constant function because the running time is always the same and not depends on the size of N.