As we learned in a previous tutorial the basic of doubly linked list.

The doubly linked list means we create a node with a 3 field which stores data and two address pointer as a previous and next node address.

Doubly circular state that our end node will point to start node and start node will point to end node to form a circular linked list.

As its circular doubly linked list initially if we have one node then that node point to itself.

Each node stores its previous and next node address, As its circular doubly linked list last node point to first and first node point to last node.

## Program

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222 | #include<stdio.h>#include<alloc.h>struct node{ int data; struct node *next; struct node *prev;}struct node *start;void insert_beg(void);void insert_end(void);void insert_before(void);void display(void);void deleteion(void);void destroy(void);#define pf printf#de4fine sc scanfvoid main(void){int ch;start=NULL;do{pf(“\n 1. insert_beg\n 2. insert_end\n 3. insert_before\n 4. Display\n 5. Deletion\n 6.Destroy\n7.Exit”);sf(“%d”,&ch);switch(ch){case 1: insert_beg(); break;case 2:insert_end();break;case 3:insert_before();break;case 4:display();break;case 5:deletion();break;case 6:destroy();break;case 7:exit(0);break;}}while(ch!=7);}void insert_beg(void){struct node *nn,*lp;nn=(strcut node *)malloc(sizeof(struct node));pf(“Enter data”);sf(“%d”,&nn->data);if(start==NULL){nn->next=nn;nn->prev=nn;start=nn;}else{lp=start->prev;nn->prev=lp;nn->next=start;start->prev=nn;lp->next=nn;start=nn;}}void insert_end(void){struct node *nn ,*lp;nn=(strcut node *)malloc(sizeof(struct node));pf(“Enter data”);sf(“%d”,&nn->data);if(start==NULL){nn->prev=nn;nn->next=nn;start=nn;}else{lp=start->prev;nn->next=start;nn->prev=lp;start->prev=nn;lp->next=nn;}}void insert_before(void){struct node *nn ,*temp,*ptemp;int x;if(start==NULL){pf(“DLL is empty”);return;}pf(“Enter data which you want to insert the node”);sf(“%d”,&x);if(x==start->data){insert_beg(); return;}temp=start;while(temp!=NULL && temp->data!=x){ptemp=temp;temp=temp->next;if(temp==start){pf(“%d does not exist:”,x);return;}}nn=(strcut node *)malloc(sizeof(struct node));pf(“Enter data”);sf(“%d”,&nn->data);nn->prev=ptemp;nn->next=temp;ptemp->next=nn;temp->prev=nn;}void display(void){struct node *temp*ptemp;if(start==NULL){pf(“\n DLL is empty”);return;}pf(“Forward order”);temp=start;do{pf(“%d”,temp->data);temp=temp->next;}while(temp!=start);temp=start->prev;pf(“reverse order”);do{pf(“%d”,temp->data);temp=temp->prev;}while(temp!=start->prev);}void deletion(void) {struct node *ptemp,*temp,*ntemp,*lp;int x;if(start==NULL){pf(“\n DLL is empty”);return;}pf(“Enter data to delete”);sf(“%d”,&x);if(x==start->data){if(start==start->next){temp=start;start=null;free(temp);}else{temp=start;lp=start->prev;start=start->next;free(temp);start->prev=lp;lp->next=start;}return;}temp=start;while(temp ->data!=x){ptemp=temp;temp=temp->next;if(temp==start){pf(“%d does not exist”);return;}}ptemp->next=temp->next;ntemp=temp->next;ntemp->prev=ptemp;free(temp);}}void destroy(void) {struct node *temp,*dp;if(start==NULL){pf(“\n DLL is empty”);return;}temp=start;while(temp!=NULL){dp=temp;temp=temp->next;free(dp);}start=NULL;} |