Sorting
Insertion sort
Selection sort
Bubble sort

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The efficiency of handling data can be substantially
improved if the data are sorted according to some criteria of
order. In a telephone directory we are able to locate a phone
number, only because the names are alphabetically ordered.
Same thing
holds true for listing of directories created by
us on the computer. It would be very annoying if we don’t
follow some order to store book indexes, payrolls, bank
accounts, customer records, items inventory records,
especially when the number of records is pretty large.
•
We want to keep information in a sensible order.
−
alphabetical order
−
ascending/descending order
−
order according to names, ids, years, departments etc.
•
The aim of sorting algorithms is to put unordered
information in an ordered form.
•
There are dozens of
sorting algorithms. The more
popular ones are listed below:
−
Selection Sort
−
Bubble Sort
−
Insertion Sort
−
Merge Sort
−
Quick Sort
As always, we want to decide which algorithms are best for
a particular situation. The efficiency is decided by the
number of comparisons and the number of data
movements, using the big-O notation.
The order of

magnitude can vary depending on the initial ordering of
data.
How much time, does a computer spend on data ordering if
the data are already ordered? We often try to compute the
data movements, and comparisons for the following three
cases:
best case ( often, data is already in order),
worst case( sometimes, the data is in reverse order),
and average case( data in random order).
Some sorting methods perform the same operations
regardless of the
initial ordering of data. Why should we
consider both comparisons and data movements?
If simple keys are compared, such
as integers or
characters, then the comparisons are relatively fast and
inexpensive. If strings or arrays of numbers are compared,
then the cost of comparisons goes up substantially.
If on the other hand, the data items moved are large, such
as structures, then the movement measure may stand out as
the determining factor in efficiency considerations.

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