Added DoublyLinked List

Author: kartikeysingh6

data_structures/C++/doubly_linkedlist.cpp

@@ -0,0 +1,92 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+class Node{
+public:
+	int data;
+	Node* prev;
+	Node* next;
+};
+
+Node* head=NULL;	//initially head is null;
+
+Node* MakeNewNode(int x) {
+	Node* newNode= new Node();	//new operator creates memory space
+	newNode->data=x;
+	newNode->prev=NULL;
+	newNode->next=NULL;
+	return newNode;
+}
+
+//Inserts a Node at head of doubly linked list
+void InsertAtHead(int x){
+	Node* newNode=MakeNewNode(x);
+	if(head == NULL){
+		head = newNode;
+		return;
+	}
+	head->prev=newNode;
+	newNode->next=head; 
+	head=newNode;
+}
+
+void InsertAtTail(int x){
+	 Node* temp=head;
+	 Node* newNode=MakeNewNode(x);
+	if(head==NULL){
+		head=newNode;
+		return;
+	}
+	while(temp->next!=NULL) 
+		temp = temp->next; // Go To last Node
+	temp->next = newNode;
+	newNode->prev = temp;
+}
+
+//prints all nodes starting from head till we find NULL
+void Print(){
+	 Node* temp=head;
+	while(temp!=NULL){
+		cout<<temp->data<<" ";
+		temp = temp->next;
+	}
+	cout<<endl;
+}
+
+//prints all nodes from last to head;
+void ReversePrint(){
+	Node* temp=head;
+	if(temp==NULL) 
+		return;
+
+	//going till we reach last 
+	while(temp->next!=NULL){
+		temp=temp->next;
+	}
+	//now from last we go backwards
+	while(temp!=NULL) {
+		cout<<temp->data<<" ";
+		temp=temp->prev;
+	}
+	cout<<endl;
+}
+
+int main(){
+	InsertAtTail(2); 
+	Print();
+	InsertAtTail(4); 
+	Print();
+	InsertAtHead(6); 
+	Print();
+	InsertAtTail(8); 
+	Print();
+	InsertAtTail(3); 
+	Print();
+	InsertAtTail(1); 
+	Print();
+	InsertAtHead(4);
+	Print();
+	ReversePrint();
+
+	return 0;
+}