Merge pull request #191 from kiruba-r11/feature-1

Added Delete At the Head of the Doubly Linked Lists

Author: smv1999

Data Structures/Linked Lists/Circular Doubly Linked Lists/delete_at_begin.cpp

@@ -0,0 +1,110 @@
+/*
+
+This is a Circular Doubly Linked List program which deletes a Node at the head of the Linked Lists.
+Since, it is a Ciruclar Doubly Linked List, both the forward and backward traversal is also possible.
+
+*/
+
+
+#include <iostream>
+
+using namespace std;
+
+/*
+
+Node definition:
+	1. Pointer to previous node.
+	2. Integer Data
+	3. Pointer to next node.
+
+*/
+
+class dcll_node {
+public:
+	dcll_node* prev;
+	int data;
+	dcll_node* next;
+};
+
+void createDCLL(dcll_node* &head) {
+
+	dcll_node* temp = head;
+
+	int choice;
+
+	do {
+
+		int data;
+
+		cout << "Enter Data : ";
+		cin >> data;
+
+		dcll_node* newNode = new dcll_node();
+		newNode->data = data;
+		newNode->prev = NULL;
+		newNode->next = NULL;
+
+		if(head == NULL) {
+			head = newNode;
+			temp = head;
+			head->next = head;
+			head->prev = head;
+		} else {
+			temp->next = newNode;
+			newNode->prev = temp;
+			temp = newNode;
+			newNode->next = head;
+			head->prev = newNode;
+		}
+
+		cout << "Do you want to continue? (1/0) : ";
+		cin >> choice;
+
+	} while(choice == 1);
+
+}
+
+void delete_at_begin(dcll_node* &head) {
+	if(head == NULL || head->next == head) {
+		head = NULL;
+		delete head;
+		return;
+	}
+
+	dcll_node* temp = head;
+	head = head->next;
+	head->prev = temp->prev;
+	temp->prev->next = head;
+	delete temp;
+}
+
+void display(dcll_node* head) {
+
+	cout << "The elements are : ";
+	dcll_node* temp = head;
+
+	do {
+
+		cout << temp->data << " ";
+		temp = temp->next;
+
+	} while(temp != head);
+	cout << endl;
+}
+
+int main() {
+
+	dcll_node* head = NULL;
+
+	createDCLL(head);
+
+	cout << "Before Deletion : " << endl;
+	display(head);
+
+	delete_at_begin(head);
+
+	cout << "After Deletion : " << endl;
+	display(head);
+
+	return 0;
+}