Naive string matching

Naive string matching

• 1.
  NAIVE STRING MATCHING PREPARED BY  ABHISHEKKUMAR SINGH
• 2.
  What is aString? In C, String is a sequence of characters or more specifically can be regarded as an array of characters.
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  String Matching One ofthe most commonest operation done with strings is String Matching.
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  WHAT IS STRINGMATCHING? If we are given a string “p” which is nothing but stream of characters p[0],p[1],p[2]……..p[n-1] (where n is the length of the string),then searching for a specific pattern in the string is known as string matching
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  Applications of StringMatching  Intrusion Detection • String matching in bioinformatics • String matching in Digital Forensics
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  An example ofstring matching Here we discuss an example on string matching where the given text consists of a pattern which is to be searched for. The following figure shows the location of pattern P in a given text T.
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  Algorithm For StringMatching There are many ways to do the String Matching but here we discuss the concept of Naïve String Matching.
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  Naive string matching Runningtime: O((n-m+1)m).
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  Problem with naivealgorithm  Whenever a character mismatch occurs after matching of several characters, the comparison begins by going back in T from the character which follows the last beginning character. This makes the process very slow. • Suppose p=ababc, T=cabababcd • T: c a b a b a b c d • P: a … • P: a b a b c • P: a… • P: a b a b c
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  Solution to theProblem There are many more algorithms which work in a more efficient way than the naive string matching and are listed below:- Rabin–Karp string search algorithm Finite-state automaton Knuth–Morris–Pratt algorithm Boyer–Moore string search algorithm
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  THANK YOU