C programs for Double ended queue ADT Using Doubly Linked List

1			#include<stdio.h>
2			#include<stdlib.h>
3			struct node
4			{
5			int data;
6			struct node *previous;
7			struct node *next;
8			};
9			struct node *front, *rear;
10			int count;
11			void display();
12			void insert_begin(int x);
13			void insert_last(int x);
14			int delete_begin();
15			int delete_last();
16			int main()
17			{
18			int ch;
19			int ele;
20			printf("\n\t1. Insert-begin\n\t2. Insert-last\n\t3. Delete-begin\n\t4. Delete-last\n\t5. Display
21			\n6.exit");
22			while(1)
23			{
24			printf("Enter_your_choice:");
25			scanf("%d",&ch);
26			switch(ch)
27			{
28			case 1:
29			printf("Enter_value_for_insertion :");
30			scanf("%d",&ele);
31			insert_begin(ele);
32			break;
33			case 2:
34			printf(" Enter_the_value_for_insertion:");
35			scanf("%d",&ele);
36			insert_last(ele);
37			break;
38			case 3:
39			ele = delete_begin();
40			if(ele!=-1)
41			printf("%d is deleted .",ele);
42			break;
43			case 4:
44			ele = delete_last();
45			if(ele!=-1)
46			printf("%d is deleted .",ele);
47			break;
48			case 5:
49			display();
50			break;
51			case 6: exit(0);
52			}
53			}
54			}
55			void display()
56			{
57			struct node * ptr;
58			ptr = front;
59			if(front==NULL || rear==NULL)
60			{
61			printf("List is empty");
62			return;
63			}
64			while(ptr != NULL)
65			{
66			printf( "%d -> ",ptr ->data);
67			ptr = ptr->next;
68			}
69			printf("\n");;
70			}
71			void insert_begin(int x)
72			{
73			struct node *new1;
74			new1 = (struct node*)malloc(sizeof(struct node));
75			new1 -> data =x;
76			new1 ->previous = new1 ->next =NULL;
77			if(front == NULL||rear==NULL)
78			front = rear = new1;
79			else
80			{
81			new1 ->next = front;
82			front ->previous = new1;
83			front = new1;
84			}
85			}
86			void insert_last(int x)
87			{
88			struct node *new1;
89			new1 = (struct node*)malloc(sizeof(struct node));;
90			new1 ->data = x;
91			new1 -> previous = new1 ->next = NULL;
92			if (front == NULL||rear==NULL)
93			front = rear = new1;
94			else
95			{
96			rear ->next = new1;
97			new1 ->previous = rear;
98			rear = new1;
99			}
100			}
101			int delete_begin()
102			{
103			int x;
104			struct node *temp;
105			if (front == NULL || rear==NULL)
106			{
107			printf( " LIST_IS_EMPTY ");
108			return -1;
109			}
110			else
111			{
112			temp = front;
113			x= temp->data;
114			if(front==rear)
115			{
116			front=NULL;
117			rear=NULL;
118			}
119			else
120			{
121			front = front->next;
122			front->previous = NULL;
123			}
124			count --;
125			free(temp);
126			return x;
127			}
128			}
129			int delete_last( )
130			{
131			int x;
132			struct node *temp;
133			if(rear == NULL || front==NULL)
134			{
135			printf( " LIST_IS_EMPTY ");
136			return -1;
137			}
138			else
139			{
140			temp = rear;
141			if(front==rear)
142			{
143			front=NULL;
144			rear=NULL;
145			}
146			else
147			{
148			rear = rear->previous;
149			rear -> next = NULL;
150			}
151			x= temp ->data;
152			free(temp);
153			count --;
154			return x;
155			}
156			}
			Output:
			1. Insert-begin
			2. Insert-last
			3. Delete-begin
			4. Delete-last
			5. Display
			6.exit
			Enter_your_choice:1
			Enter value for insertion :10
			Enter_your_choice:2
			Enter_the_value_for_insertion:20
			Enter_your_choice:5
			10 -> 20 ->
			Enter_your_choice:1
			Enter_value_for_insertion :30
			Enter_your_choice:5
			30 -> 10 -> 20 ->
			Enter_your_choice:2
			Enter_the_value_for_insertion:40
			Enter_your_choice:5
			30 -> 10 -> 20 -> 40 ->
			Enter_your_choice:3
			30 is deleted .
			Enter_your_choice:5
			10 -> 20 -> 40 ->
			Enter_your_choice:4
			40 is deleted .
			Enter_your_choice:5
			10 -> 20 ->
			Enter_your_choice:6