Create and flip a one-way linked list

Thanks to XX's written examination, I finally made up my mind to thoroughly think about this seemingly simple question. I found my understanding was really unsatisfactory!

 

The following chain table flip is achieved by re-creating a new chain table. The space complexity is too low...

# Include <iostream> <br/> using namespace STD; <br/> struct node <br/> {<br/> int data; <br/> node * next; <br/>}* head; <br/> void addnode (INT value); <br/> void swap (node * & head); <br/> int main () <br/>{< br/> head = NULL; <br/> addnode (1); <br/> addnode (2); <br/> addnode (3 ); <br/> addnode (4); <br/> addnode (5); <br/> addnode (6); <br/> node * P = head; <br/> while (p) <br/>{< br/> cout <p-> data <"; <br/> P = p-> next; <br/>} <Br/> swap (head); <br/> P = head; <br/> cout <Endl; <br/> while (P) <br/>{< br/> cout <p-> data <""; <br/> P = p-> next; <br/>}< br/> system ("pause"); <br/> return 0; <br/>}< br/> void addnode (INT value) <br/>{< br/> node * P = new node (); <br/> P-> DATA = value; <br/> P-> next = NULL; </P> <p> If (! Head) <br/>{< br/> head = P; <br/>}< br/> else <br/>{< br/> node * q = head; <br/> while (Q-> next) <br/> q = Q-> next; <br/> q-> next = P; <br/>}< br/> void swap (node * & head) <br/>{< br/> node * qold = head; <br/> node * phead = new node (); <br/> If (! Head) <br/>{< br/> cout <"The linked list is empty! "<Endl; <br/> return; <br/>}< br/> phead-> DATA = head-> data; </P> <p> phead-> next = NULL; <br/> while (qold-> next) <br/>{< br/> node * pnew = new node (); <br/> * pnew = * (qold-> next ); <br/> pnew-> next = phead; <br/> phead = pnew; <br/> qold = qold-> next; <br/>}< br/> head = phead; <br/>}< br/>

Improvement: Use the legendary three-pointer method ~

Void swap (node * & head) <br/>{< br/> If (! Head) <br/>{< br/> cout <"The linked list is empty! "<Endl; <br/> return; <br/>}< br/> node * A [3]; <br/> A [0] = A [1] = NULL; <br/> A [2] = head; <br/> while (A [2]-> next) <br/>{< br/> A [0] = A [1]; <br/> A [1] = A [2]; <br/> A [2] = A [2]-> next; <br/> A [1]-> next = A [0]; </P> <p >}< br/> A [2]-> next = A [1]; <br/> head = A [2]; <br/>}