Doubly linked list (non-circular) related operations: Create, destructor, delete, bubble sort

structdulnode{intVal; Dulnode*Pre; Dulnode*next;};//This is not a double-loop linked list.dulnode* Create_dulnode (intN) {    if(N <=0)returnNULL; inti =0; Dulnode*head, *P1, *P2; //Build head NodeHead =NewDulnode; Head->val = rand ()%Rand_max; Head->pre = NULL;//the head node precursor node is emptyP1 =Head;  for(i =1; I < n; i++) {P2=NewDulnode; P2->val = rand ()%Rand_max; P2->pre =P1; P1->next =P2; P1=P2; } p1->next =NULL; returnhead;}voidDel_dulnode (dulnode* &head,Const intnum) {    //The linked list is empty    if(NULL = = head)return; Dulnode*temp, *p; //Delete head node     while(head! = Null&&num = = head->val) {Temp=Head; Head= head->Next; Head->pre =NULL; Deletetemp; cout<<"To Delete a head node:"<< Num <<Endl; } P=Head;  while(P! =NULL) {        if(num = = p->val) {Temp=p; P->pre->next = temp->Next; P= temp->Next; Deletetemp; cout<<"To Delete a node:"<< Num <<Endl; }        Else{p= p->Next; }    }}voidErase_dulnode (dulnode*head) {    if(NULL = = head)return; Dulnode*temp, *p =Head;  while(p) {Temp=p; P= p->Next; Deletetemp; }}voidPrint_dulnode (dulnode*head) {    if(NULL = = head)return; inti =0; Dulnode*p =Head;  while(p) {cout<<" "<< P->val <<","; P= p->Next; if(5== ++i) {i=0; cout<<Endl; }} cout<<Endl;}intGetdulnodelistlen (dulnode*head) {    if(NULL = = head)return 0; intn =0; Dulnode* p=Head;  while(p) {++N; P= p->Next; }    returnN;}voidSortdulnodelist (dulnode*head) {    //empty double-linked list or single-node doubly linked list does not operate    if(NULL = = Head | | NULL = = Head->next)return; BOOLSign =false; intI, j, len =Getdulnodelistlen (head), temp; Dulnode*p;  for(i = len-1; i >0; i--) { sign=false; P=Head;  for(j =0; J < I; J + +)        {            if(P->val > p->next->val) {Temp= p->Val; P->val = p->next->Val; P->next->val =temp; Sign=true; } P= p->Next; }        if(!sign) Break;//This loop has no value exchange and the sorting is complete    }}

Doubly linked list (non-circular) related operations: Create, destructor, delete, bubble sort