Merge pull request pranjay-poddar#183 from Saksham188/master

AddedDoublyLinkedList

Author: pranjay-poddar

c++/DoublyLinkedList.cpp

@@ -0,0 +1,118 @@
+#include<iostream>
+using namespace std;
+
+///In this we have 2 pointers next and previous at every node.
+
+class Node
+{
+public:
+    int Data;
+    Node* next;
+    Node* prev;
+
+    Node(int Value)
+    {
+        Data= Value;
+        next=NULL;
+        prev=NULL;
+    }
+};
+
+///Here we are inserting at the head of Linked List.
+void InsertAtHead(Node* &head,int Value)
+{
+     Node* n=new Node(Value);
+
+     n->next=head;
+     if(head!=NULL)   ///its because if head  is null then we can't access its previous.
+     {
+        head->prev=n;
+     }
+
+     head=n;
+}
+///Here we are inserting at the tail of Linked List.
+void InsertAtTail(Node* &head,int Value)
+{
+    if(head==NULL)
+    {
+        InsertAtHead(head,Value);
+        return;
+    }
+    Node* n= new Node(Value);
+
+    Node* temp=head;
+
+    while(temp->next!=NULL)
+    {
+        temp=temp->next;
+    }
+    temp->next=n;
+    n->prev=temp;  
+}
+///Here we are displaying complete Linked List.
+void Display(Node* head)
+{
+    Node* n=head;
+
+    while(n->next!=NULL)
+    {
+        cout<<n->Data<<"->";
+        n=n->next;
+    }
+    cout<<"NULL"<<endl;
+}
+///Here we are deleting at the head of Linked List.
+void DeleteAtHead(Node* &head)
+{
+    Node* todelete=head;
+    head=head->next;
+    head->prev=NULL;
+
+    delete todelete;
+}
+
+///Here we are deleting at particular position of Linked List.
+void Deletion(Node* &head,int pos)
+{
+    if(pos==1)
+    {
+        DeleteAtHead(head);
+        return;
+    }
+    Node* temp=head;
+    int Count=1;
+    while(temp!=NULL && Count!=pos)
+    {
+        temp=temp->next;
+        Count++;
+    }
+    temp->prev->next=temp->next;
+
+    if(temp->next!=NULL)   
+    {
+       temp->next->prev=temp->prev;
+    }
+
+
+    delete temp;
+}
+
+
+int main()
+{
+    Node* head=NULL;
+    InsertAtTail(head,1);
+    InsertAtTail(head,2);
+    InsertAtTail(head,3);
+    InsertAtTail(head,4);
+    InsertAtTail(head,5);
+    Display(head);
+    InsertAtHead(head,6);
+    InsertAtHead(head,7);
+    InsertAtHead(head,8);
+    Display(head);
+
+    Deletion(head,1);
+    Display(head);
+}