C++ how to reverse singly linked list

[KENNY LIU]

My class

 
 
#ifndef NODE_H
#define NODE_H
 
#include <cstdlib> // Provides size_t and NULL
 
class Node
{
public:
 
// TYPEDEF
typedef int value_type;
 
// CONSTRUCTOR
Node(const value_type& init_data = value_type(), Node* init_link = NULL)
{
data_field = init_data; 
link_field = init_link;
}
 
// Member functions to set the data and link fields:
void set_data(const value_type& new_data) 
{
data_field = new_data;
}
 
void set_link(Node* new_link) 
{
link_field = new_link;
}
 
// Constant member function to retrieve the current data:
value_type data() const 
{
return data_field;
}
 
// Two slightly different member functions to retreive
// the current link. Similar to next()
const Node* link() const 
{
return link_field;
}
 
Node* link() 
{
return link_field;
}
 
private:
value_type data_field;
Node* link_field;
};
 
size_t list_length(const Node* head_ptr)
{
const Node *cursor;
size_t answer;
 
answer = 0;
for(cursor = head_ptr; cursor != NULL; cursor = cursor->link())
++answer;
 
return answer;
}
 
#endif
 
 

My problem:

Write a function to split a singly linked list L into two smaller linked lists P and Q.
The length of L is unknown and the splitting point should be the middle of L. Assume that L has at least two nodes.

What I have:

 
void split(const Node* L, Node*& P, Node*& Q)
{
int i = 0;
int L_mid = list_length(L)/2;
 
const Node *tmp = L;
 
for(i=0;i<L_mid;tmp=tmp->link(),++i)
{    
}
 
P = L;
Q=tmp;
tmp->link()=NULL;
 
}
 
 

I'm not sure what to do. Any help is appreciated. Thanks

[weaknessforcats]

It might help if you write the steps you are going to take on paper before starting to code. Like:

1) make a pass of L and count he nodes
2) locate midpoint of L
etc...