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Knuth-Morris-Pratt Algorithm.

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Presentation on theme: "Knuth-Morris-Pratt Algorithm."— Presentation transcript:

1 Knuth-Morris-Pratt Algorithm

2 Knuth – Morris – Pratt algorithm is a PATTERN matching algorithm

3 Knuth – Morris – Pratt algorithm is used to search a pattern in a text

4 Knuth – Morris – Pratt algorithm
was introduced in 1974 by Donald Knuth and Vaughan Pratt, and independently by James H. Morris

5 Knuth – Morris – Pratt algorithm
was jointly published by all three, in 1977

6 Knuth – Morris – Pratt algorithm
We use two terms, Pattern and Text Pattern Word which we want to search Text Data in which we want to search for pattern

7 Every character in Pattern is compared with characters in Text
How does KMP work Every character in Pattern is compared with characters in Text If all characters in Pattern are matching with characters in text, then search success If any mismatch found then, shift the pattern according to Prefix Table and continue with comparison

8 What is Prefix Table Example
A table derived for Pattern, which specifies “How many positions the pattern has to shift” when we found mismatch Example Index 1 2 3 4 5 6 Pattern A B C D A B D Shifting Value 1 2 1

9 How to create Prefix Table
A prefix table is created using length of substrings in pattern Example Index 1 2 3 4 5 6 Pattern A B C D A B D Shifting Value 1 1 2 2 1 1

10 How to create Prefix Table
A prefix table is created using length of substrings in pattern Example Index 1 2 3 4 5 6 Pattern A B C D A B D Shifting Value 1 1 2 2 1 1


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