[Algorithm and data structure] _ 8 _ linear structure _ string _ pattern matching _ continued _ 1

In fact, the exhaustion method of pattern matching can also be improved. The following is an improved method.Code.

[Improve version]

The strmatchimp () function is an improved function.

 /*  BenProgramTest various processing functions and operations of strings  */  # Include <Stdio. h> # Include <Stdlib. h> # Include < String . H> //  **************************************** * ************** 0  // Define User Data Types Typedef Long   Int  Lint; typedef  Enum  {False, true} bool;  //  **************************************** * ************** 1  //  **************************************** * ************** 0  Int Stringmatch ( Char * String, Char * Substring,Int  Startindex );  Int Stringmatchrecall ( Char * String, Char * Substring, Int  Startindex );  Int Strmatchimp ( Char * String , Char * Substring, Int  Startindex );  Int Main (Int Argc, Char * Argv []) {  Int  X; x = Stringmatch ( "  Abcdefghijklmn  " , "  Lm  " , 0  ); Printf (  "  % D \ n  " , X); x = Stringmatchrecall ( "  Abcdefghijklmn  " , "  X  " , 0  ); Printf (  "  % D \ n  "  , X); x = Strmatchimp ( "  Abcdefghijklmn  " , "  Lm  " , 0  ); Printf (  "  % D \ n  "  , X); getchar ();  Return   0  ;}  //  **************************************** * ************** 1  // **************************************** * ************** 0  /*  Function: simple pattern matchingAlgorithm: Dual-cycle function prototype: int stringmatch (char * string, char * substring, int startindex) function parameter: char * string: String char * substring: mode string int startindex: search Start index return value: If the match is successful, the first address of the pattern string starting in the string is returned; if the match fails, the-1 exception is returned: None  */  Int Stringmatch ( Char * String, Char * Substring, Int  Startindex ){  Int I, J;  Int  Strlen, substrlen; strlen = Strlen (string); substrlen = Strlen (substring );  //  Check pointer validity and empty string  //  In fact, startindex> strlen (string)-strlen (substring) cannot be detected here)      If (! String |! Substring |! String [ 0 ] |! Substring \ | Startindex> strlen-Substrlen \)  Return - 1  ;  For (I = startindex; I <= strlen-substrlen; I ++ ){  For (J = 0 ; J <substrlen; j ++ ){  If (String [I + J]- Substring [J])  Break  ;} If (J = substrlen) //  This is because the loop to be ended is exactly equal.              Return ++ I; //  I ++ cannot be used in this place.  }  Return - 1  ;}  //  **************************************** * ************** 1  //  **************************************** * ************** 0 /*  Function function: simple pattern matching algorithm: single-cycle backtracking function prototype: int stringmatchrecall (char * string, char * substring, lint startindex) function parameter: char * string: String char * substring: pattern string int startindex: Index start return value: If the match is successful, return the first address of the pattern string starting in the string; if the match fails, return-1 exception: None  */  Int Stringmatchrecall ( Char * String, Char * Substring, Int  Startindex ){  Int  I, J;  Int Strlen, substrlen; strlen = Strlen (string); substrlen = Strlen (substring );  //  Check pointer validity and empty string  //  In fact, startindex> strlen (string)-strlen (substring) cannot be detected here)      If (! String |! Substring |! String [ 0 ] |! Substring \ | Startindex> strlen- Substrlen \)  Return -1  ; I = Startindex; j = 0  ;  While (I < Strlen ){  If (String [I] = Substring [J]) { ++ J; ++ I ;}  Else  {I = I-j +1 ; //  Backtracking J = 0  ;}  If (J = Substrlen)  Return I-j + 1  ;}  Return - 1  ;}  //  **************************************** * ************** 1 //  **************************************** * ************** 0  /*  Function: String mode matching example: int strmatchimp (char * string, char * substring, int startindex) function parameter: char * string: String char * substring: pattern string int startindex: Return Value of the first index: If the match is successful, the index + 1 matching the first character is returned. Exception: None  */  Int Strmatchimp ( Char * String , Char * Substring, Int  Startindex ){ Int  I, J;  Int  Strlen, substrlen; strlen = Strlen ( String  ); Substrlen = Strlen (substring );  //  Check pointer validity and empty string  //  In fact, startindex> strlen (string)-strlen (substring) cannot be detected here)      If (! String |! Substring |! String [ 0 ] |! Substring \ | Startindex> strlen- Substrlen \)  Return - 1  ;  For (I = startindex; I <= strlen-substrlen; I ++ ){  For (J = 0 ; J <substrlen; j ++ ){  If ( String [I + J]- Substring [J])  Break  ;  Else  {  //  If the first character of the mode, substring [0], has been matched,  //  Determines whether the last character substring [SubStrLen-1] matches  //  And so on. In this way, the efficiency can be improved at the best time,  //  O (M * n) is required in the worst case)                  If (String [I + substrlen- 1 -J]-substring [substrlen- 1 - J])  Break  ;}}  If (J = substrlen) //  In this case, because the end loop is exactly the same, substring [J] = '\ 0' can also be used'              Return ++ I; //  I ++ cannot be used in this place.  }  Return - 1  ;}  //  **************************************** * ************** 1  //  **************************************** * ************** 0  /*  Function: calculates the largest matching string in the substring from the End Node to the header node. function prototype: int getmaxsubstringlen (const char * string) function parameter: const char * string: string return value: If yes, the maximum length is returned; otherwise, the-1 exception is returned: None  */  Int Getmaxsubstringlen ( Const   Char *String  ){  Return - 1  ;}  //  **************************************** * ************** 1 

The program running result is as follows:

This is complicated. You need to continue learning.