Programmers must know: C/C ++ interview questions (10)

From: http://wxdlut.blog.163.com/blog/static/12877015820099237557679/

 

The reversal of a one-way linked list is a frequently asked interview question, which is also a very basic question. For example, a linked list is like this: 1-> 2-> 3-> 4-> 5, and then 5-> 4-> 3-> 2-> 1.

The easiest way to traverse the linked list is to use an auxiliary pointer to store the next element pointed to by the current pointer during the traversal process. After the pointer of the element on the current node is reversed, use the stored pointer to traverse the backend. The source code is as follows:

Struct linka { Int daTa; Linka * next; }; Void reverse (linka * & head ){ If (Head = NULL) Return; Linka * pre, * cur, * ne; Pre = head; Cur = head-> next; While (cur) { Ne = cur-> next; Cur-> next = pre; Pre = cur; Cur = ne; } Head-> next = NULL; Head = pre; }

There is also a method that uses recursion. The basic idea of this method is to call recursive functions to reverse the subsequent nodes before reversing the current node. The source code is as follows. However, this method has one disadvantage: The last node after the inversion will form a ring, so the next field of the node returned by the function must be set to NULL. I used a reference to change the head pointer. The source code of the algorithm is as follows:

Linka * reverse (linka * p, linka * & head) { If (P = NULL | p-> next = NULL) { Head = P; Return P; } Else { Linka * TMP = reverse (p-> next, head ); TMP-> next = P; Return P; } }

② Known String classes are defined as follows:

Class string { Public: String (const char * STR = NULL); // common Constructor String (const string & Another); // copy the constructor ~ String (); // destructor String & operater = (const string & RHs); // value assignment function PRIVATE: Char * m_daTa; // used to save strings };

Try to write out the member function implementation of the class.

Answer:

String: String (const char * str)
{
If (str = NULL) // if the strlen parameter is NULL, an exception is thrown.
{
M_daTa = new char [1];
M_daTa [0] = '\ 0 ';
}
Else
{
M_daTa = new char [strlen (str) + 1];
Strcpy (m_daTa, str );
}

}

String: String (const String & another)
{
M_daTa = new char [strlen (another. m_daTa) + 1];
Strcpy (m_daTa, other. m_daTa );
}

String & String: operator = (const String & rhs)
{
If (this = & rhs)
Return * this;
Delete [] m_daTa; // Delete the original data and open a new memory
M_daTa = new char [strlen (rhs. m_daTa) + 1];
Strcpy (m_daTa, rhs. m_daTa );
Return * this;
}

String ::~ String ()
{
Delete [] m_daTa;
}