Merge pull request #431 from Soumyajit2411/master

Double circular linked list implementation

Author: amritansh22

double_circular_linkedlist.cpp

@@ -0,0 +1,136 @@
+#include<iostream>
+#include<stdlib.h>
+using namespace std;
+
+struct node
+{
+    int data;
+    struct node *next;
+    struct node *prv;
+};
+
+void create(struct node **h)
+{
+    int n,i;
+    printf("How many elements you want to enter: ");
+    scanf("%d",&n);
+    struct node *ptr=NULL;
+    for(i=0;i<n;i++)
+    {
+        struct node *cur=(struct node *)malloc(sizeof(struct node));
+        cur->data=rand()%10;
+        cur->next=NULL;
+        cur->prv=NULL;
+
+        if(*h==NULL)
+        {
+            *h=cur;
+            cur->next=cur->prv=cur;
+            ptr=cur;
+        }
+        else 
+        {
+            cur->prv=ptr;
+            ptr->next=cur;
+            cur->next=*h;
+            ptr=cur;
+        }
+    }
+
+} 
+
+void display(struct node *h)
+{   
+    struct node *cur;
+    printf("linked list:\t");
+  for(cur=h;cur->next!=h;cur=cur->next)
+  {
+      printf("%d\t",cur->data);
+  }
+  printf("%d",cur->data);
+}
+
+void insert(struct node **h,int x,int p)
+{
+    struct node *cur;
+    struct node *ptr;
+    cur=(struct node *)malloc(sizeof(struct node));
+    cur->data=x;
+    cur->next=cur->prv=NULL;
+    
+    if(*h==NULL)
+    {
+        *h=cur;
+        cur->next=cur->prv=cur;
+    }
+    else if(p==0)
+    {
+       cur->next=*h;
+       cur->prv=(*h)->prv;
+       (*h)->prv->next=cur;
+       (*h)->prv=cur;
+       *h=cur;
+    }
+    else
+    {
+        ptr=*h;
+        int i=1;
+        while(i<p && ptr->next!=*h)
+        {
+            ptr=ptr->next;
+            i++;
+        }
+        cur->next=ptr->next;
+        cur->prv=ptr;
+        ptr->next->prv=cur;
+        ptr->next=cur;
+    }
+
+}
+
+void del(struct node **h,int p)
+{
+    struct node *ptr;
+    struct node *cur;
+    if(*h==NULL)
+    {
+        printf("EMPTY");
+    }
+    else if(p==0)
+    {
+        for(ptr=*h;ptr->next!=*h;ptr=ptr->next){}
+
+        ptr->next=(*h)->next;
+        cur=*h;
+        *h=(*h)->next;
+        (*h)->next->prv=ptr;
+        free(cur);   
+    }
+    else
+    {
+        ptr=*h;
+        int i=1;
+        while(i<p && ptr->next!=*h)
+        {
+            cur=ptr;
+            ptr=ptr->next;
+            i++;
+        }
+        cur->next=ptr->next;
+        ptr->next->prv=cur;
+        free(ptr);
+    }
+}
+
+int main()
+{
+    struct node *head=NULL;
+    create(&head);
+    display(head);
+    insert(&head,2,6);
+    display(head);
+    printf("\n");
+    del(&head,0);
+    display(head);
+    return 0;
+}