need some help

[Joe Wright]

Re: need some help

shailesh.budhan er@gmail.com wrote:[color=blue]
> Hi
> u can use strstr function which returns int telling position of first
> occurance of one string in other string
> by using that position(index) u can return poiter.
> ash wrote:
>[/color]
On my system, string.h has an entry..

char * strstr(const char *_s1, const char *_s2);

...suggesting strstr does not return int.

--
Joe Wright
"Everything should be made as simple as possible, but not simpler."
--- Albert Einstein ---

[av]

Re: need some help

On Sat, 10 Jun 2006, "Malcolm" <regniztar@btin ternet.com> wrote:[color=blue]
>"ash" <ashishmourya21 @rediffmail.com > wrote[color=green]
>> one friend advised me to use "strstr" function, this is a easy way to
>> solve that question by use built in function but actually i was trying
>> to make this function and i want help in writing that function.
>>[/color]
>First write the skeleton
>
>/*
> mystrstr - find the first occurrence of substring in string
> Params: substring - string to search for
> string - string to search in.
> Returns: pointer to occurence of substring in string, NULL if none found.
>*/
>char *mystrstr(char *substring, char *string)
>{
>}
>
>Now for the algorithm.[/color]

easy if i have the right book

#include <stdio.h>
#include <stdlib.h>

#define F for
#define R return
#define W while
#define P printf
#define G goto
#define uns unsigned

// cerca in una stringa "a" la sottostringa "p"
// la stringa da cercare "p" deve essere di lunghezza
// minore di 1023 chars
// se errore: qualche stringa è il vettore nullo, oppure
// se errore di lunghezza massima di "p" (>=1023chars) ritorna 0
//
// altrimenti ritorna un puntatore alla stringa "a"
// ove ha trovato la sottostringa "p" o eventualmente
// (se non l'ha trovata) punta alla fine di "a" in &a[len]
char* kmns(char* p, char* a)
{int i,j, k;
int next[1024];
if(p==0||a==0) R 0;
F(i=0, j=-1, next[0]=-1; p[i]&&i<1023; )
{W(j>=0 && p[i]!=p[j] ) j=next[j];
++i; ++j;
next[i]=((j>=0&&p[i]==p[j])?next[j]:j);
}
if(i>=1023) R 0;
F(k=0, j=0; j<i&&a[k]; ++j, ++k)
W(j>=0 && a[k]!=p[j]) j=next[j];
R (j==i? a+(k-i): a+k);
}


// cerca in un FILE* "a" la stringa "p"
// la stringa da cercare "p" deve essere si lunghezza
// minore di 1022 chars
// se stringa non trovata ritorna 0
// se stringa trivata ritorna 1
// se errore in qualsiasi fase ritorna -1
int kmnsf(char* p, FILE* a)
{int i,j, k;
int next[1024], c;
if(p==0||a==0) R -1;
F(i=0, j=-1, next[0]=-1; p[i]&&i<1023; )
{W(j>=0 && p[i]!=p[j] ) j=next[j];
++i; ++j;
next[i]=((j>=0&&p[i]==p[j])?next[j]:j);
}
if(i>=1023) R -1;
F(j=0; j<i&&(c=getc(a) )!=EOF; ++j)
W(j>=0 && c!=p[j]) j=next[j];
R (j==i? 1: 0);
}


/* Pacific Standard Time & Daylight Savings */
// char *tzstr = "TZ=PST8PDT ";

int main(void)
{char *sub;

sub=kmns("Fred" , "My name is Fred and i am dead");
// should print "Fred and i am dead"
P("1 sub=[%s]\n", (sub==0? "NULL":sub) );
sub=kmns("Frede rick", "My name is Fred and i am dead");
P("2 sub=[%s]\n", (sub==0? "NULL":sub) );
// should print out that sub is NULL
sub = kmns("Frederick ", "Fred");
P("3 sub=[%s]\n", (sub==0? "NULL":sub) );
// Null here too
sub=kmns("Fred" , "Fred is Fred dead?");
// here "Fred is Fred dead"
P("4 sub=[%s]\n", (sub==0? "NULL":sub) );
// here "Fred is Fred dead"
sub=kmns("Fred" , sub+1);
P("5 sub=[%s]\n", (sub==0? "NULL":sub) );
// here "Fred dead"

exit(0);
}

C:>string
1 sub=[Fred and i am dead]
2 sub=[]
3 sub=[]
4 sub=[Fred is Fred dead?]
5 sub=[Fred dead?]

[CBFalconer]

Re: need some help

av wrote:[color=blue]
>[/color]
.... snip ...[color=blue]
>
> easy if i have the right book
>
> #include <stdio.h>
> #include <stdlib.h>
>
> #define F for
> #define R return
> #define W while
> #define P printf
> #define G goto
> #define uns unsigned[/color]

RosIwhatzis has reappeared under another name. PLONK

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http://www.netmeister.org/news/learn2quote.html

[Default User]

Re: need some help

av wrote:


[color=blue]
> #define F for
> #define R return
> #define W while
> #define P printf
> #define G goto
> #define uns unsigned[/color]

Skunk cabbage by any other name . . .

*plonk*



Brian

[av]

Re: need some help

On Sun, 11 Jun 2006 11:08:02 +0200, av <av@ala.a> wrote:
[color=blue]
>#include <stdio.h>
>#include <stdlib.h>
>
>#define F for
>#define R return
>#define W while
>#define P printf
>#define G goto
>#define uns unsigned
>
>// cerca in una stringa "a" la sottostringa "p"
>// la stringa da cercare "p" deve essere di lunghezza
>// minore di 1023 chars
>// se errore: qualche stringa è il vettore nullo, oppure
>// se errore di lunghezza massima di "p" (>=1023chars) ritorna 0
>//
>// altrimenti ritorna un puntatore alla stringa "a"
>// ove ha trovato la sottostringa "p" o eventualmente
>// (se non l'ha trovata) punta alla fine di "a" in &a[len]
>char* kmns(char* p, char* a)
>{int i,j, k;
> int next[1024];
> if(p==0||a==0) R 0;
> F(i=0, j=-1, next[0]=-1; p[i]&&i<1023; )
> {W(j>=0 && p[i]!=p[j] ) j=next[j];
> ++i; ++j;
> next[i]=((j>=0&&p[i]==p[j])?next[j]:j);[/color]

is it better here next[i]=(p[i]==p[j]?next[j]:j); ?
i say yes. j should be >0 here or not?

[color=blue]
>int kmnsf(char* p, FILE* a)
>{int i,j, k;
> int next[1024], c;
> if(p==0||a==0) R -1;
> F(i=0, j=-1, next[0]=-1; p[i]&&i<1023; )
> {W(j>=0 && p[i]!=p[j] ) j=next[j];
> ++i; ++j;
> next[i]=((j>=0&&p[i]==p[j])?next[j]:j);[/color]

the same here
[color=blue]
> }
> if(i>=1023) R -1;
> F(j=0; j<i&&(c=getc(a) )!=EOF; ++j)[/color]