Analysis and implementation of C-language function strstr ()

The following is a detailed analysis of the use of strstr () function in C language, the need for friends can refer to the next

Prototype: Char *strstr (const char *STR1, const char *STR2);
#include <string.h>
finds the first occurrence of the STR2 string in the STR1 string (excluding the STR2 string terminator). Returns a pointer to the position, such as if it is not found, and returns a null pointer.
Returns a pointer to the ' the ' of strsearch in str, or NULL if Strsearch does is not appear in Str. ifstrsearch PO INTs to a string of zero length, the function returns STR.

Copy Code code as follows:


#include &lt;stdio.h&gt;


#include &lt;conio.h&gt;


#include &lt;string.h&gt;


#include &lt;stdlib.h&gt;


#pragma warning (disable:4996)


Char *mystrstr (char *s1,char *s2);


int main (void)


{


Char *s= "Golden Global View";


char *l= "OB"; Char *l= ""


Char *p;


System ("CLS");


P=mystrstr (s,l);


if (p!=null)


 {


printf ("%sn", p);


 }


Else


 {


printf ("Not found!n");


 }


Getch ();


return 0;


}


/*from Encyclopedia * *


Char *mystrstr (char *s1,char *s2)


{


int n;


if (*S2)//Two situation considerations


 {


while (*S1)


  {


for (n=0;* (s1+n) ==* (s2+n); n++)


{


if (!* (s2+n+1))//lookup next character is '
'

    {


return (char*) S1;


    }


            }


s1++;


  }


return NULL;


 }


Else


 {


return (char*) S1;


 }


}

Another implementation:

Copy Code code as follows:


char * STRSTR (BUF, sub)


Register char *buf;


Register char *sub;


{


Register char *BP;


Register char *sp;


if (!*sub)


return buf;


while (*BUF)


    {


bp = buf;


sp = sub;


do {


if (!*SP)


return buf;


} while (*bp++ = = *sp++);


buf + + 1;


    }


return 0;


}

Another implementation:

Copy Code The code is as follows:

#include <iostream>
#include <string>
using namespace std;
//c Language Implementation strstr
Const char* Issub (const char* STR, const char *subs) {
 //special case
 if (!*subs)
  return str;
  Const char* TMP=STR;
 while (*tmp!= ')
 {
  //is used to move the parent string back one character at a time
  const char* tmp1=tmp;
& nbsp; //The record substring address
  const char* sub1=subs;
  while (*sub1!= ' &&*tmp1!= ')
  {
   //If not equal jumps out, moves the parent string one character back
   if (*SUB1!=*TMP1)
     break;
   //If equal and the next character at the end of the substring is the substring of the parent string
   if (*sub1==*tmp1&&* (sub1+1) = = ")
    return tmp;
   //continues to compare the next character if equal
   if (*SUB1==*TMP1)
   {
     sub1++;
    tmp1++;
   }
  }
  tmp++;
 }
 return NULL;
}
int main () {
 char* str1= "Ababcdddb";
 char* str= "";
 const Char *res=issub (STR1, STR);
 if (res!=null)
 {
  cout << res << endl;
 }
 else
&nb Sp; cout << "null" << Endl;
 //cout << issub (str1,str) << Endl;
 return 0;
}