string matching algorithms
TRANSCRIPT
STRING MATCHING ALGORITHMS
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OUTLINE
What is String?
What is String Matching?
Definition of Algorithm
String Matching Algorithms
String Matching Algorithms Applications
WHAT IS STRING?
In computer programming, a string is traditionally a
sequence of characters, either as constant or as
some kind of variable
E.g. ABCABDC or 1Ac35D
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WHAT IS STRING?
String may be applied in Bioinformatics to describe
DNA strand composed of nitrogenous bases
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WHAT IS STRING MATCHING?
String matching is finding occurrence(s) of a pattern
string within another string or body of text
E.g. We have a string “BCATDOG” and the pattern
to be searched is “CAT”. Now finding “CAT” in the
string “BCATDOG” is string matching
WHAT IS STRING MATCHING?
Uses for the string matching include:
Finding a text in a document file or in a report
Used by different search engines like: Google
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EXAMPLE
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DEFINITION OF ALGORITHM
Algorithm is formula or set of rules followed for
solving a problem.
Example: Searching algorithms, sorting algorithms,
etc.
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Example: Algorithm for checking a lamp
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STRING MATCHING ALGORITHMS
Brute Force Algorithm
Karp-Rabin Algorithm
Boyer-Moore Algorithm
BRUTE FORCE ALGORITHM
Simplest string matching algorithm
Steps:
Match the first character of the pattern with the first
character of the string
If succeed, try to match the second character, and then
third and so on
BRUTE FORCE ALGORITHM
If hit a failure point, slide the pattern over one character
and try again
When a match is found, return its starting location
Example:
Given string “BCCATDOG”
Pattern to match is “CAT”
EXAMPLE
ALGORITHM FOR EXAMPLE
Step1: Match the first character of the pattern with the first character of the string
Step3: If hit a failure point, slide the pattern over one character and try again
Step2: If succeed, try to match the next character, and so on
Step4: When a match is found, return its starting location
Starting location for the pattern in the string is “3”
STRING MATCHING ALGORITHMS
APPLICATIONS
Besides Computer Science, String matching
algorithms have some other applications:
Detecting Plagiarism:
it is the process of locating instances of
plagiarism within a work or document
Bioinformatics
String algorithms are centrally important in
bioinformatics for dealing with sequence
information
CONT.
Molecular biology
Approximate matching of a search pattern to
a target text is a fundamental tool in
molecular biology
Computer Science
Exact string matching is more useful in
computer science
CONT.
Text Mining Research:
includes information extraction, topic
tracking, content summarization, information
visualization, question answering, concept
linkage, text classification, and text clustering
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