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Knuth-Morris-Pratt Pattern Matching Algorithm

Knuth-Morris-Pratt Pattern Matching Algorithm. Instructor : Prof. Jyh-Shing Roger Jang Designer ： Shao-Huan Wang The ideas are reference to the textbook “Fundamentals of Data Structures in C “ and “ 名題精選百則 - 使用 C 語言 ( 技巧篇 )”. Knuth-Morris-Pratt Pattern Matching Algorithm.

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Knuth-Morris-Pratt Pattern Matching Algorithm

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  1. Knuth-Morris-PrattPattern Matching Algorithm Instructor : Prof. Jyh-Shing Roger Jang Designer：Shao-Huan Wang The ideas are reference to the textbook “Fundamentals of Data Structures in C “ and “名題精選百則-使用C語言(技巧篇)”.

  2. Knuth-Morris-PrattPattern Matching Algorithm • Use failure function

  3. Knuth-Morris-PrattPattern Matching Algorithm • Use failure function First, initial f(0) = -1

  4. Knuth-Morris-PrattPattern Matching Algorithm • Use failure function -1 First, initial f(0) = -1 j++, i = f(j-1), then compare p[i+1] and p[j] If p[i+1] != p[j] and f(i-1) == -1, put -1

  5. Knuth-Morris-PrattPattern Matching Algorithm • Use failure function 0 1 First, initial f(0) = -1 j++, i = f(j-1), then compare p[i+1] and p[j] If p[i+1] != p[j] and f(i-1) == -1, put -1 Else if p[i+1] == p[j], put i+1 Else if p[i+1] != p[j] and i != -1, let i = f(i), until p[i+1] == p[j] or i == -1

  6. Knuth-Morris-PrattPattern Matching Algorithm • Use failure function -1 Not equal! First, initial f(0) = -1 j++, i = f(j-1), then compare p[i+1] and p[j] If p[i+1] != p[j] and f(i-1) == -1, put -1 Else if p[i+1] == p[j], put i+1 Else if p[i+1] != p[j] and i != -1, let i = f(i), until p[i+1] == p[j] or i == -1 If i == -1 compare p[0] and p[j]

  7. Knuth-Morris-PrattPattern Matching Algorithm • Use failure function 0 1 2 3 First, initial f(0) = -1 j++, i = f(j-1), then compare p[i+1] and p[j] If p[i+1] != p[j] and f(i-1) == -1, put -1 Else if p[i+1] == p[j], put i+1 Else if p[i+1] != p[j] and i != -1, let i = f(i), until p[i+1] == p[j] or i == -1 If i == -1 compare p[0] and p[j]

  8. Knuth-Morris-PrattPattern Matching Algorithm • Use failure function 2 Not equal! Equal! First, initial f(0) = -1 j++, i = f(j-1), then compare p[i+1] and p[j] If p[i+1] != p[j] and f(i-1) == -1, put -1 Else if p[i+1] == p[j], put i+1 Else if p[i+1] != p[j] and i != -1, let i = f(i), until p[i+1] == p[j] or i == -1 If i == -1 compare p[0] and p[j] If p[i+1] == p[j], put i+1

  9. Knuth-Morris-PrattPattern Matching Algorithm • Use failure function 0 Not equal! First, initial f(0) = -1 j++, i = f(j-1), then compare p[i+1] and p[j] If p[i+1] != p[j] and f(i-1) == -1, put -1 Else if p[i+1] == p[j], put i+1 Else if p[i+1] != p[j] and i != -1, let i = f(i), until p[i+1] == p[j] or i == -1 If i == -1 compare p[0] and p[j] If p[i+1] == p[j], put i+1 If i == -1 and p[0] == p[j], put i+1

  10. Knuth-Morris-PrattPattern Matching Algorithm • Use failure function First, initial f(0) = -1 j++, i = f(j-1), then compare p[i+1] and p[j] If p[i+1] != p[j] and f(i-1) == -1, put -1 Else if p[i+1] == p[j], put i+1 Else if p[i+1] != p[j] and i != -1, let i = f(i), until p[i+1] == p[j] or i == -1 If i == -1 compare p[0] and p[j] If p[i+1] == p[j], put i+1 If i == -1 and p[0] == p[j], put i+1

  11. Knuth-Morris-PrattPattern Matching Algorithm • Use failure function • Compare with a string s[] : Compare with s[i] and p[j], start with i = j = 0 If s[i] != p[j] and j != 0, j = f(j-1)+1

  12. Knuth-Morris-PrattPattern Matching Algorithm • Use failure function • Compare with a string s[] : Compare with s[i] and p[j], start with i = j = 0 If s[i] != p[j] and j != 0, j = f(j-1)+1 Else if s[i] != p[j] and j == 0, i++

  13. Knuth-Morris-PrattPattern Matching Algorithm • Use failure function • Compare with a string s[] : Compare with s[i] and p[j], start with i = j = 0 If s[i] != p[j] and j != 0, j = f(j-1)+1 Else if s[i] != p[j] and j == 0, i++

  14. Knuth-Morris-PrattPattern Matching Algorithm • Use failure function • Compare with a string s[] : Compare with s[i] and p[j], start with i = j = 0 If s[i] != p[j] and j != 0, j = f(j-1)+1 Else if s[i] != p[j] and j == 0, i++

  15. Knuth-Morris-PrattPattern Matching Algorithm • Use failure function • Compare with a string s[] : Compare with s[i] and p[j], start with i = j = 0 If s[i] != p[j] and j != 0, j = f(j-1)+1 Else if s[i] != p[j] and j == 0, i++

  16. Knuth-Morris-PrattPattern Matching Algorithm • Use failure function • Compare with a string s[] : Compare with s[i] and p[j], start with i = j = 0 If s[i] != p[j] and j != 0, j = f(j-1)+1 Else if s[i] != p[j] and j == 0, i++

  17. Knuth-Morris-PrattPattern Matching Algorithm • Use failure function • Compare with a string s[] : Compare with s[i] and p[j], start with i = j = 0 If s[i] != p[j] and j != 0, j = f(j-1)+1 Else if s[i] != p[j] and j == 0, i++ Following the rules and you can finish this comparison

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