Merge pull request #725 from Monik09/DoubleEndedQueue

Added DoubleEndedQueue[C]

Author: theyashshahs

double_ended_queue/doubleEndedQueue.c

@@ -0,0 +1,156 @@
+#include <stdlib.h>
+#include <stdio.h>
+
+struct Deque
+{
+	int data;
+	struct Deque *next;
+};
+struct Deque *head = NULL;
+struct Deque *last = NULL;
+
+struct Deque *createDeque(struct Deque *root, int key)	//Function to create deque
+{
+	root = (struct Deque *)malloc(sizeof(struct Deque));
+	root->data = key;
+	root->next = NULL;
+	head = root;
+	last = root;
+	return head;
+}	//O(1) time complexity
+
+struct Deque *push_front(struct Deque *root, int key)	//Function to push element on the front of deque
+{
+	if (head == NULL)
+	{
+		return createDeque(root, key);
+	}
+	struct Deque *temp;
+	temp = (struct Deque *)malloc(sizeof(struct Deque));
+	temp->data = key;
+	temp->next = head;
+	head = temp;
+	return head;
+}	//O(1) time complexity
+
+struct Deque *push_back(struct Deque *root, int key)	//Function to push element to the back of deque
+{
+	if (head == NULL)
+	{
+		return createDeque(root, key);
+	}
+	struct Deque *temp;
+	temp = (struct Deque *)malloc(sizeof(struct Deque));
+	temp->data = key;
+	temp->next = NULL;
+	last->next = temp;
+	last = temp;
+	return last;
+}	//O(1) time complexity
+
+struct Deque *pop_front()	//Function to remove or pop the front element
+{
+	if (head == NULL)
+	{
+		printf("Deque is empty.\n");
+		return head;
+	}
+	struct Deque *temp;
+	temp = head;
+	head = head->next;
+	free(temp);	//free the unwanted space
+	return head;
+}	//O(1) time complexity
+
+struct Deque *pop_back()	//Function to remove element from back of deque
+{
+	if (head == NULL)	//before removing element, checking whether the deque is empty or not
+	{
+		printf("Deque is empty\n");
+		return head;
+	}
+	struct Deque *temp, *temp2;
+	temp = head;
+	while (temp->next != last)
+	{
+		temp = temp->next;
+	}
+	temp2 = temp->next;
+	temp->next = NULL;
+	last = temp;
+	free(temp2);//free the unwanted space
+	return head;
+}	//O(n) time complexity
+
+void front()	//Function to give the front element of deque
+{
+	if (head == NULL)
+	{
+		printf("Deque is empty.\n\n");
+	}
+	printf("The element at the front of deque is %d.\n\n", head->data);
+}	//O(1) time complexity
+
+void back()	//Function to give the back of deque
+{
+	if (head == NULL)
+	{
+		printf("Deque is empty\n");
+	}
+	printf("The element at the last of deque is %d.\n\n", last->data);
+}	//O(1) time complexity
+
+void isEmpty()	//Function to know whether deque is empty or not
+{
+	if (head == NULL)
+	{
+		printf("List is empty.\n\n");
+	}
+	else
+	{
+		printf("No, list is not empty.\n\n");
+	}
+}	//O(1) time complexity
+
+void displayTheDeque()	//Function to print the whole deque
+{
+	if (head == NULL)
+	{
+		printf("Deque is empty.\n\n");
+	}
+	else
+	{
+		printf("The Deque is \n\t ");
+		printf("Front-----> ");
+		struct Deque *temp = head;	//initializing the temporary pointer to head of deque
+		while (temp != NULL)
+		{
+			printf("%d  \t", temp->data);
+			temp = temp->next;
+		}
+		printf(" <-----End\n\n");
+	}
+}	//O(n) time complexity
+
+int main()
+{
+	struct Deque *root = NULL;
+	root = createDeque(root, 4);	//creating Deque
+	push_front(root, 6);	//pushing data on the front
+	push_back(root, 5);	//pushing data on the back
+	push_front(root, 61);
+	push_front(root, 6);
+	push_front(root, 12);
+	push_front(root, 60);
+	push_back(root, 68);
+	displayTheDeque();	//Displaying the deque
+	pop_front();	//removing front element
+	printf("After removing from front, ");
+	displayTheDeque();
+	pop_back();	//removing back element
+	printf("After removing from back, ");
+	displayTheDeque();
+	front();	//Getting value of front element of deque
+	back();	//Getting value of back element of deque
+	isEmpty();	//Checking if deque is empty or not
+}