Interpretation of growth-rate functions
1 -- A growth rate function 1 implies a problem whose time requirement is constant and, therefore independent of problem size.
log2N -- Time requirement for a logarithmic algorithm increases slowly as the problem size increases. For example, if you square the problem size you only double the time requirement.
N -- Linear algorithm: Time requirement increases directly with the size of the problem.
N-squared: Quadratic. Algorithms that use two nested loops are examples.