The infamous Bubble Sort is O(N^{2}).
So is quicksort, in the worst case. :) Mergesort and heapsort are both O(N log N) in the worst case.
Most of the time, there's no difference in asymptotic order between the average and worstcase inputs, but every once in a while, something (like quicksort) comes along and bites you on the ass on certain inputs. Quicksort expects its input to be mostly random; ordered input will mess it up. (Think about building a binary tree from ordered input: you'll get a linear list, which is O(N) nodes deep, not a nice bushy tree, which would be O(log N) nodes deep.) Something to think about when building divide and conquer algorithms.

F
o
x
t
r
o
t
U
n
i
f
o
r
m
Found a typo in this node? /msg me
The hell with paco, vote for Erudil!
Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
Read Where should I post X? if you're not absolutely sure you're posting in the right place.
Please read these before you post! —
Posts may use any of the Perl Monks Approved HTML tags:
 a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
Outside of code tags, you may need to use entities for some characters:

For: 

Use: 
 &   & 
 <   < 
 >   > 
 [   [ 
 ]   ] 
Link using PerlMonks shortcuts! What shortcuts can I use for linking?
See Writeup Formatting Tips and other pages linked from there for more info.

