int j = 0 , k = -1 ;

		next[0] = -1 ;

		while ( j < (int)strlen(str) )
		{
			if ( k == -1 || str[j] == str[k] )
			{
				j++ ;
				k++ ;
				next[j] = k ;
			}
			else
				k = next[k] ;
		}