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searching a string

 
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searching a string
Artaniz
post 5 Dec, 2005 - 11:13 AM
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i need to search a string then return how far is the char is.

i know how to search for a single char, but the program requires that we search for a whole word or more than 1 letter.

he is what it is supposed to look like.

Enter state: Tennesse
Enter term: es

Tennesse, es - 4





my problem is that if i search for 'es' then it finds the first instance of 'e' but not the whole term 'es'

heres my code it only loops once so far.


CODE
char str[] = "tennessee";
 char par[] = "es";
 int i;
 i = strcspn (str,par);
 cout <<"The differnce in "<< str <<" between " << par << " is " << i << endl;
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Nova Dragoon
post 5 Dec, 2005 - 11:16 AM
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look for examples of the naive-string matcher algorithm, or the KMP-Matcher algoritm

the naive uses 2 nested for-loops

the outer keeps track of index of the string you are searching in
the inner keeps track of the index of the string you are searching for
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Artaniz
post 5 Dec, 2005 - 11:21 AM
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? i have never hear do that?

what is it, where is it...

heres the main prob. if i enter an 'e' to search within 'Tennessee', it find the first 'e' which is correct. but if i enter 'es' then it only searches for the 'e' and forgets the 's'
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Nova Dragoon
post 5 Dec, 2005 - 11:23 AM
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google search
"naive string matcher"

Here is one of the first things tha pops up
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Artaniz
post 5 Dec, 2005 - 11:29 AM
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i found something but of course it is way to complex for me

CODE

/* Naive Strint Matching Algorithm
   strMatch(T,P)
   - match whether P is substring of T
   - return the starting index of the first occurence of P in T
*/

#include <cstdio>
int strMatch(char *T,char *P)
{
   int i,j,n,m,found;
   n = strlen(T);
   m = strlen(P);
             
   for (i=0; i<=n-m; i++)
   {
       found = 1;
       for (j=0; j<m; j++)
          if (P[j] != T[i+j])
          {
              found = 0;
              break;
          }
       if (found) return i;
   }
   return -1;
}


i dont understand this can you help me anyalize it or explian it to me

This post has been edited by Artaniz: 5 Dec, 2005 - 11:30 AM
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Nova Dragoon
post 5 Dec, 2005 - 02:18 PM
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T is the string you are searching in
P is the pattern string you are searching for


The outter loop steps through T character by character
The inner loop steps through P character by character

firs the outer loop, sets found to one (true), if in the inner loop, the
pattern doesnt match up, found is set to zero


The inner loop starts comparring P[j] with T[I+J] starting from I in T
do this for all J=size of P

If there is not a match on one, fail, and start that the next I in T.

If success, return I = the possition of the match
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born2c0de
post 5 Dec, 2005 - 08:02 PM
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You can use the strstr function from string.h
That will only tell you if a sub-string exists in a string and returns a pointer that points to the character where the match occurs.
You can subtract the pointer addresses to get the position of occurance.
But of course, I'd prefer the naive-string searcher algorithm.
This is an alternative.
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Artaniz
post 7 Dec, 2005 - 11:00 AM
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ok i have studied the algorothm and have used it in my program and it works. thanks for all the help
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