C language: customizes a function for searching strings, similar to strstr (), string. hstrstr in & lt; string. h & gt;

C language: customizes a function for searching strings, similar to strstr (), string. hstrstr in <string. h>.

// Customize a string to search for the standard library function strstr ()

# Include <stdio. h>

# Include <string. h>

Char * myStrstr (char * str1, char * str2 );

Int main ()

{

Char * str1 = "hello worl world ld ";

Char * str2 = "world ";

Puts (myStrstr (str1, str2 ));

Return 0;

}

Char * myStrstr (char * str1, char * str2)

{

Static int count = 0;

Const char * p = str2;

Char * pt;

While (* (str2 ++ ))

{

While (* (str1 ++ ))

{

// If the first character of str2 and str1 is the same, and then the second character is compared, count is accumulated.

If (* (str2-1) = * (str1-1 ))

{

Count ++;

Break;

}

// If the first character of str2 and str1 is different, traverse str1 until the end

Else if (* (str2-1 )! = * (Str1-1) & count <strlen (p ))

{

Continue;

}

// If the first few characters of str2 and str1 are the same, str2 starts from scratch.

Else

{

Str2 = str2-count;

Break;

}

}

If (* str2 = '\ 0' & count = strlen (p ))

Pt = str2-count; // locate the string, move the pointer to the first address of str2 and return

Else

Pt = NULL; // the string is not found and NULL is returned.

}

Return pt;

}