Merge pull request #140 from kiruba-r11/feature-1

Added program to Delete a Node from the beginning in a Doubly Linked Lists

Author: smv1999

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

@@ -0,0 +1,107 @@
+/*
+
+This is a Doubly Linked List program which deletes a node at the beginning to the Linked List.
+Since, it is a 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 dll_node {
+public:
+	dll_node* prev;
+	int data;
+	dll_node* next;
+};
+
+void createDLL(dll_node* &head) {
+
+	int choice;
+
+	dll_node* temp = head;
+
+	do {
+
+		int data;
+
+		cout << "Enter Data : ";
+		cin >> data;
+
+		dll_node* newNode = new dll_node();
+		newNode->data = data;
+		newNode->prev = NULL;
+		newNode->next = NULL;
+
+		if(head == NULL) {
+			head = newNode;
+			temp = head;
+		} else {
+			temp->next = newNode;
+			newNode->prev = temp;
+			temp = newNode;
+		}
+
+		cout << "Do you want to continue? (1/0) : ";
+		cin >> choice;
+
+	} while(choice == 1);
+
+
+}
+
+void delete_at_begin(dll_node* &head) {
+
+	if(head == NULL)
+		return;
+
+	if(head->next == NULL) {
+		dll_node* temp = head;
+		head = head->next;
+		delete temp;
+		return;
+	}
+
+	dll_node* temp = head;
+	head = head->next;
+	head->prev = NULL;
+	delete temp;
+	return;
+
+}
+
+void display(dll_node* head) {
+	cout << "The elements are : ";
+	while(head != NULL) {
+		cout << head->data << " ";
+		head = head->next;
+	}
+	cout << endl;
+}
+
+int main() {
+
+	dll_node* head = NULL;
+
+	createDLL(head);
+
+	cout << "Before Deletion : " << endl;
+	display(head);
+
+	delete_at_begin(head);
+
+	cout << "After Deletion : " << endl;
+	display(head);
+
+	return 0;
+}