String Matching Algorithms-The Naive Algorithm
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String matching algorithms are used to find patterns within larger strings or texts. The example shows a text string "A B C A B A A C A B" and a pattern "A B A A" with a shift of 3. The naive string matching algorithm is described which compares characters between the text and pattern from index 0 to the string lengths to find all valid shifts where the pattern occurs in the text.
![THE NAIVE ALGORITHM
T[n]=T[0,1âŠn-1]
P[m]=P[0,1âŠm-1]
NAIVE-STRING-MATCHER(T,P)
1) n = T.length
2) m = P.length
3) for s=0 to n-m
4) if P[0âŠm-1]==T[s+0âŠ.s+m-1]
5) printâ Pattern occurs with shift â s](https://image.slidesharecdn.com/stringmatchingalgorithms-thenaivealgorithm-180718073714/85/String-Matching-Algorithms-The-Naive-Algorithm-7-320.jpg)
String Matching Algorithms-The Naive Algorithm
- 1. STRING MATCHING ALGORITHMS A B C A B A A C A B SHIFT=3 A B A A
- 2. BY: Adeel Rasheed ï For More Slides and Information Visit: ï https://chauhantricks.blogspot.com/
- 3. WHAT IS STRING MATCHING âą In computer science, string searching algorithms, sometimes called string matching algorithms, that try to find a place where one or several string (also called pattern) are found within a larger string or text.
- 4. EXAMPLE STRING MATCHING PROBLEM TEXTA B C A B A A C A B SHIFT=3 A B A A
- 5. Types of SMA ï The Naive string-matching algorithm ï The Rabin-Krap algorithm ï String matching with finite automata ï The Knuth-Morris-Pratt algorithm
- 6. THE NAIVE ALGORITHM ï The idea of the naive solution is just to make a comparison character by character of the text for all pattern. ï It returns all the valid shifts found. ï P=Pattern ï T=Text ï S=Shift
- 7. THE NAIVE ALGORITHM T[n]=T[0,1âŠn-1] P[m]=P[0,1âŠm-1] NAIVE-STRING-MATCHER(T,P) 1) n = T.length 2) m = P.length 3) for s=0 to n-m 4) if P[0âŠm-1]==T[s+0âŠ.s+m-1] 5) printâ Pattern occurs with shift â s
- 8. EXAMPLE SUPPOSE, T=1011101110 P=111 FIND ALL VALIDSHIFTâŠâŠ 1 0 1 1 1 0 1 1 1 0 1 1 1P=Patter n T=Text S=0
- 9. 1 0 1 1 1 0 1 1 1 0 1 1 1 S=1
- 10. 1 0 1 1 1 0 1 1 1 0 1 1 1 S=2 So, S=2 is a valid shiftâŠ
- 11. 1 0 1 1 1 0 1 1 1 0 S=3 1 1 1
- 12. 1 0 1 1 1 0 1 1 1 0 S=4 1 1 1
- 13. 1 0 1 1 1 0 1 1 1 0 1 1 1 S=5
- 14. 1 0 1 1 1 0 1 1 1 0 S=6 1 1 1 So, S=6 is a valid shiftâŠ
- 15. 1 0 1 1 1 0 1 1 1 0 1 1 1 S=7