programming-for-dummies

Chapter 2: Searching Algorithms
In This Chapter
Conducting sequential and binary tree searches
Using an index
Comparing search algorithms
One of the most common functions of a computer program is searching.
A database needs to search through names and addresses, a word
processor needs to search through text, and even a computer chess game
needs to search through a library of moves to find the best one.
Because searching is such an important part of computer programming,
computer scientists have developed a variety of algorithms to search for
data. When searching for data, the main limitation is time. Given enough
time, any search algorithm can find what you want, but there’s a big difference
between finding data in five seconds or five hours.
The time a search algorithm takes is always related to the amount of data to
search, which is the search space. The larger the search space, the slower
the search algorithm. If you only need to search a small search space, even a
simple and slow search algorithm is fast enough.
The two main categories of search algorithms are
✦ Uninformed (or brute-force)
✦ Informed (or heuristic)
Uninformed, or brute-force, search algorithms work by simply examining the
entire search space, which is like losing your car keys in your apartment and
searching every apartment in the entire building. Eventually, you find your
keys, but it may take a long time to do it.
Informed, or heuristic, search algorithms work by selectively examining the
most likely parts of the search space. This is like losing your car keys in your
apartment but only examining the bedroom where you last saw your car keys.
By using knowledge of the search space, informed search algorithms can speed
up a search algorithm by eliminating obvious parts of the search space that
don’t contain the data you want to find.