Bidirectional loop Linked list (C + + implementation)

In this bidirectional circular list, the header node first does not have an element, and when the bidirectional loop list is empty:first->rlink=first->llink=first;

The following code realizes the insertion and deletion of the bidirectional circular linked list, and in the insert operation, the head interpolation method and the sequential insertion method are implemented.

//main.cpp//----------Establish a two-way circular link list-------#include<iostream>Using namespace Std;class dblist;class dblistnode{friend class DBList;Private: intData; Dblistnode*Llink,*Rlink;}; Class dblist{ Public: DBList ()//Using a constructor to create a circular linked list with a head node (no element stored){First=NewDblistnode (); First -Llink=First -Rlink=First };voidInsert1 (int);voidInsert2 (int);voiddel (int);voidShow ();Private: Dblistnode*First;};voidDBList:: Insert1(int x)//Insert element with head interpolation, note the order of insertion steps{Dblistnode*P=NewDblistnode (); P -Data=X P -Rlink=First -Rlink;//Insertion Step (1)P -Llink=First//Insertion Step (2)First -Rlink -Llink=P//Insertion Step (3)First -Rlink=P//Insertion Step (4)}voidDBList:: Insert2(int x)//Insert elements sequentially, note the order of insertion steps{Dblistnode*P=NewDblistnode (); P -Data=X Dblistnode*Q=First -Rlink;if(q==First//When the double-linked list is empty, insert it at the top of the chain{p -Rlink=First P -Llink=First First -Llink=P First -Rlink=P }Else{ while(q -Rlink!=First&&Q -Data<=x) {Q=Q -Rlink; }if(q -Data>X//Intermediate insertion{p -Rlink=Q//Insertion Step (1)P -Llink=Q -Llink;//Insertion Step (2)Q -Llink -Rlink=P//Insertion Step (3)Q -Llink=P//Insertion Step (4)}Else          //When the insertion position is at the end of the chain{p -Rlink=First P -Llink=Q First -Llink=P Q -Rlink=P }     }}voidDBList::d el(int x) {Dblistnode*Q=First -Rlink; while(q!=First&&Q -Data!=X//Starting from the first element to find{Q=Q -Rlink; }if(q!=First//Find x{Q -Llink -Rlink=Q -Rlink;//Perform a delete operationQ -Rlink -Llink=Q -Llink;  Delete q; }Else{cout<<"x cannot be found, cannot be deleted"<<Endl }}voidDBList:: Show() {Dblistnode*P=First -Rlink; cout<<"list element is:"; while(p!=First) {cout<<P -Data<<" "; P=P -Rlink; } cout<<Endl;}  int main () {dblist l1,l2; L1.Insert1 ( -); L1.Insert1 ( -); L1.Insert1 ( +); L1.Insert1 ( -); L1.Show (); cout<<"After removing element 40"<<Endl L1.Del +); L1.Show (); L2.Insert2 ( -); L2.Insert2 ( -); L2.Insert2 ( +); L2.Insert2 ( -); L2.Show (); cout<<"After removing element 40"<<Endl L2.Del +); L2.Show (); System"Pause");return 0;}

Bidirectional loop Linked list (C + + implementation)