Implementation example of string matching KMP algorithm in php

The kmp algorithm is an improved string matching algorithm. e. knuth and V. r. pratt and J. h. morris also discovered that it was called the Knut -- Morris -- Pratt operation (KMP algorithm ). The key to the KMP algorithm is to define a next function based on the given pattern string W1, m. The next function contains information about local matching of the pattern string.

Example

The code is as follows:

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<? Php /* PHP implementation of string matching KMP algorithm */ Function KMP ($ str ){ $ K = array (0 ); $ M = 0; $ StrLen = strlen ($ str ); For ($ I = 1; $ I <$ strLen; $ I ++ ){ If ($ str [$ I] ==$ str [$ M]) { $ K [$ I] = $ K [$ i-1] + 1; $ M ++; } Else { $ M = 0; $ K [$ I] = $ K [$ M];         }     } Return $ K; }   // KMP search Function KMPMatch ($ src, $ par ){ $ K = KMP ($ par );   $ SrcLen = strlen ($ src ); $ ParLen = strlen ($ par );   For ($ I = 0, $ j = 0; $ I <$ srcLen ;){            // Returns the exact matched position. If ($ j = $ parLen) return $ I-$ j;            // Print the matching process Echo $ I. "". $ j. "{$ src [$ I]}-{$ par [$ j]} <BR> ";   If ($ par [$ j] ===$ src [$ I]) {              // Record matching count $ J ++; $ I ++; } Else { If ($ j = 0 ){ $ I ++;             } $ J = $ K [$ J-1> = 0? $ J-1: 0];         }     } Return false; }   // Test availability $ Src = 'BBC ABCDAB abcdababd '; $ Par = 'ABCD ';   // Matching value Echo "partially matched values:", implode ("", KMP ($ par), "<BR> "; // Search for specific characters (strings) in a given string) Echo KMPMatch ($ src, $ par), "<BR> ";   /* Partial matching value: 0 0 0 0 1 2 0 0 0 B-A B-A 1 0 C-A 2 0 3 0- 4 0 A-A 1 B-B 6 2 C-C 7 3 D-D 8 4 A-A 9 5 B-B 10 6-D 10 2-C 10 0- A-A 11 0 12 B-B C-C 13 2 14 3 D-D 15 4 A-A 16 5 B-B C-D 17 6 17 2 C-C 18 3 D-D 19 A-A 20 5 B-B D-D 21 6 15 */