circular linked list insertion

1#include <stdio.h>
2#include <string.h>
3#include <stdlib.h>
4#include <stdbool.h>
5
6struct node {
7   int data;
8   int key;
9	
10   struct node *next;
11};
12
13struct node *head = NULL;
14struct node *current = NULL;
15
16bool isEmpty() {
17   return head == NULL;
18}
19
20int length() {
21   int length = 0;
22
23   //if list is empty
24   if(head == NULL) {
25      return 0;
26   }
27
28   current = head->next;
29
30   while(current != head) {
31      length++;
32      current = current->next;   
33   }
34	
35   return length;
36}
37
38//insert link at the first location
39void insertFirst(int key, int data) {
40
41   //create a link
42   struct node *link = (struct node*) malloc(sizeof(struct node));
43   link->key = key;
44   link->data = data;
45	
46   if (isEmpty()) {
47      head = link;
48      head->next = head;
49   } else {
50      //point it to old first node
51      link->next = head;
52		
53      //point first to new first node
54      head = link;
55   }    
56}
57
58//delete first item
59struct node * deleteFirst() {
60
61   //save reference to first link
62   struct node *tempLink = head;
63	
64   if(head->next == head) {  
65      head = NULL;
66      return tempLink;
67   }     
68
69   //mark next to first link as first 
70   head = head->next;
71	
72   //return the deleted link
73   return tempLink;
74}
75
76//display the list
77void printList() {
78
79   struct node *ptr = head;
80   printf("\n[ ");
81	
82   //start from the beginning
83   if(head != NULL) {
84	
85      while(ptr->next != ptr) {     
86         printf("(%d,%d) ",ptr->key,ptr->data);
87         ptr = ptr->next;
88      }
89   }
90	
91   printf(" ]");
92}
93
94void main() {
95   insertFirst(1,10);
96   insertFirst(2,20);
97   insertFirst(3,30);
98   insertFirst(4,1);
99   insertFirst(5,40);
100   insertFirst(6,56); 
101
102   printf("Original List: "); 
103	
104   //print list
105   printList();
106
107   while(!isEmpty()) {            
108      struct node *temp = deleteFirst();
109      printf("\nDeleted value:");  
110      printf("(%d,%d) ",temp->key,temp->data);
111   }   
112	
113   printf("\nList after deleting all items: ");
114   printList();   
115}

1#include <iostream>
2
3using namespace std;
4class node
5{
6public:
7    int data;
8    node*next;
9};
10node*head=NULL;
11void insert_begin(int a)
12{
13    node*temp=new node;
14    temp->data=a;
15    if(head==NULL)
16    {
17        temp->next=temp;
18        head=temp;
19    }
20    else
21    {
22        node*ptr=new node;
23        ptr=head;
24        while(ptr->next!=head)
25        {
26           ptr=ptr->next;
27        }
28        ptr->next=temp;
29        temp->next=head;
30        head=temp;
31
32    }
33}
34void insert_end(int a)
35{
36    node*temp=new node;
37    temp->data=a;
38    if(head==NULL)
39    {
40        temp->next=head;
41        head=temp;
42    }
43    else
44    {
45        node*ptr=new node;
46        ptr=head;
47        while(ptr->next!=head)
48        {
49            ptr=ptr->next;
50        }
51        ptr->next=temp;
52        temp->next=head;
53    }
54}
55void printf()
56{
57    node*temp=new node;
58    temp=head;
59    do
60    {
61        cout<<temp->data<<" ";
62        temp=temp->next;
63    }while(temp!=head);
64
65    cout<<endl;
66}
67
68int main()
69{
70    while(1)
71    {
72        cout<<"1-insert at begin"<<endl<<"2-insert at end"<<endl<<"3-exit"<<endl;
73        int n;
74        cout<<"enter your choice:"<<endl;
75        cin>>n;
76        cout<<"enter thee value you want to insert:"<<endl;
77        int val;
78        cin>>val;
79        switch(n)
80        {
81        case 1:
82            {
83                cout<<"enter thee value you want to insert:"<<endl;
84                  int val;
85                  cin>>val;
86                insert_begin(val);
87                printf();
88                break;
89            }
90        case 2:
91            {
92                cout<<"enter thee value you want to insert:"<<endl;
93                int val;
94                cin>>val;
95                insert_end(val);
96                printf();
97                break;
98            }
99        case 3:
100
101            {
102                exit(0);
103            }
104        default:
105            {
106                cout<<"invalid choice :"<<endl;
107            }
108        }
109    }
110    return 0;
111}
112