CareerCup

#include <iostream>
using namespace std;

int main()
{
char *t = "This is lib";
char *p = "HSC";

char *s, *soln;
soln = NULL;

s = p;
int count = strlen(p);
cout<< " the strlen is " << count;

while(*t != '\0')
{
if(*t == *p)
{
t++;
p++;
if(*p == '\0')
{
soln = t - count;
}
}
else
{
p = s;
t++;
}
}
if(soln == NULL)
{
cout << "pattern not present";
}
else
cout<<"pattern found at " << soln;

return 0;

}

Please comment on my logic n implementation

Any comments on improving my implementation are welcome!

char* my_strstr(const char* s1, const char* s2)
{
char* p1 = const_cast<char*>(s1);
char* p2 = const_cast<char*>(s2);
int len = 0;

while(*p1)
{
if(*p1 == *p2)
{
p2++;
len++;
}
else
{
if(*p2 == '\0')
{
return p1-len;
}
}

p1++;
}

if(*p1==*p2)
return p1-len;

return NULL;
}

int main ()
{

  char * str1 = "mmmmmmmmmgood" ;
  char * str2 = "mmmgood" ;


  char * p =  str1 ;
  char * p2 = str2 ;
  char * start = NULL ;

  while ( *p != '\0' && *p2 != '\0')
  {
      if( *p == *p2){
         p2++ ;
         if( start == NULL) start = p ;
         p++ ;
      }
      else if ( start != NULL){
         //reset
         p2 = str2 ;
         start = NULL ;
     }
     else
        p++ ;
  }


  printf ("%s = " , start) ;

}

int strcmp(const char *a, const char *b)
{
    assert(a && b); 
    while (*a == *b) {
        if (!*a) {
            return 0;
        }
        a++; b++;
     }
     return (*a < *b) ? 1 : -1;
}

char *my_strstr(const char *str1, const char *str2)
{
char *cp = (char *)str1;
char *s1, *s2;

if(!*str2)
return (char *)str1;

while(*cp)
{
s1 = cp;
s2 = (char *)str2;

while(*s1 && *s2 && !(*s1 - *s2))
{
s1++;
s2++;
}
if(!*s2)
return(cp);
cp++;
}
return NULL;
}

char *my_strstr(const char *str1, const char *str2)
{
	char *cp = (char *)str1;
	char *s1, *s2;

	if(!*str2)
		return (char *)str1;

	while(*cp)
	{
		s1 = cp;
		s2 = (char *)str2;

		while(*s1 && *s2 && !(*s1 - *s2))
		{
			s1++;
			s2++;
		}
		if(!*s2)
			return(cp);
		cp++;
	}
	return NULL;	
}

General comment regarding some of these code snippets -- what's with the casting of const char * to a char *?? You'll need to understand the difference between char * const (or const char * const) and const char * to pass any interview I give. In none of these cases the input string is, or should be, modified. Leave the const be!

Here is the java brute force solution

// Return: Starting position of n within h or -1 if n don't occur within h
// h = main String        eg: needle
// n = search string      eg: eed
int strstr(String h, String n)
{
   if (n.length > h.length)
   {
       return -1;
   }
   
   // O(n^2) soln
   // Lets save some time instead of iterating through the whole h.
   // If h is 8 chars, and n is 5 characters, don't need to check 4th character.
   for (int i = 0; i <= (h.length - n.length) ; i++) 
   {
       int j = 0;
       for (j < n.length; j++)
       {
           if (h.charAt(i + j) != n.charAt(j))
           {
               break;
           }           
       }
       if (j == n.length)
       {
           return i;
       }       
   }
}

char *strstr(const char *s1, const char *s2) {
  const char *a = s1, *b = s2;
  for (;;) 
    if (!*b)          return (char *)s1;
    else if (!*a)          return NULL;
    else if (*a++ != *b++) {a = ++s1; b = s2;}
}

int strstr(String h, String n)
{
if (n.length > h.length)
{
return -1;
}

// O(n^2) soln
// Lets save some time instead of iterating through the whole h.
// If h is 8 chars, and n is 5 characters, don't need to check 4th character.
for (int i = 0; i <= (h.length - n.length) ; i++)
{
int j = 0;
for (j < n.length; j++)
{
if (h.charAt(i + j) != n.charAt(j))
{
break;
}
}
if (j == n.length)
{
return i;
}
}
}