queue using [ll and array] and stack using ll

data_structures/queues/C/queue_using_array.c

@@ -0,0 +1,76 @@
+#include <stdio.h>
+#include <stdlib.h>
+#define MAX 10
+
+int A[MAX];
+int front = -1;
+int rear = -1;
+
+void enqueue()
+{
+	if ((rear+1)%MAX == front)
+	{
+		printf("Can't Insert! FULL\n");
+		return;
+	}
+
+	if (front == -1)
+	{
+		front++;
+	}
+	printf("Enter data: ");
+	scanf("%d", &A[(rear+1)%MAX]);
+}
+
+void dequeue()
+{
+	if (front == -1)
+	{
+		printf("Empty!\n");
+		return;
+	}
+	if (front == rear)
+	{
+		printf("data: %d\n", A[front]);
+		front = -1;
+		rear = -1;
+		return;
+	}
+	printf("data: %d\n", A[(rear+1)%MAX]);
+}
+
+void atFront()
+{
+	if (front == -1)
+	{
+		printf("Empty!\n");
+		return;
+	}
+	printf("At the top: %d\n", A[front]);
+}
+
+int main()
+{
+	int choice;
+
+	while(1)
+	{
+		printf("1. Enqueue\n2. Dequeue\n3. At front\n4. Exit\n\nEnter Choice: ");
+	scanf("%d", &choice);
+		switch(choice)
+		{
+			case 1: 
+				enqueue();
+				break;
+			case 2:
+				dequeue();
+				break;
+			case 3:
+				atFront();
+				break;
+			default:
+				exit(0);
+		}
+	}
+
+}

data_structures/queues/C/queue_using_linkedlist.c

@@ -0,0 +1,78 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+struct node {
+	int data;
+	struct node *next;
+};
+
+struct node* front = NULL, *rear = NULL;
+
+void enqueue()
+{
+	struct node* temp = (struct node* )malloc(sizeof(struct node));
+	printf("Enter data: ");
+	scanf("%d", &temp->data);
+	temp->next = NULL;
+
+	if (front == NULL)
+	{
+		front = rear = temp;
+		return;
+	}
+
+	rear->next = temp;
+	rear = temp;
+}
+
+void dequeue()
+{
+	if (front == NULL)
+	{
+		printf("Empty!\n");
+		return;
+	}
+	struct node* temp = front;
+	printf("data: %d\n", front->data);
+	if (front == rear)
+		front = rear = NULL;
+	else 
+		front = front->next;
+	free(temp);
+}
+
+void atFront()
+{
+	if (front == NULL)
+	{
+		printf("Empty!\n");
+		return;
+	}
+	printf("At the top: %d\n", front->data);
+}
+
+int main()
+{
+	int choice;
+
+	while(1)
+	{
+		printf("1. Enqueue\n2. Dequeue\n3. At front\n4. Exit\n\nEnter Choice: ");
+	scanf("%d", &choice);
+		switch(choice)
+		{
+			case 1: 
+				enqueue();
+				break;
+			case 2:
+				dequeue();
+				break;
+			case 3:
+				atFront();
+				break;
+			default:
+				exit(0);
+		}
+	}
+
+}

data_structures/stacks/C/stack_using_linked_list.c

@@ -0,0 +1,78 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+struct node {
+	int data;
+	struct node *next;
+};
+
+struct node* front = NULL, *rear = NULL;
+
+void enqueue()
+{
+	struct node* temp = (struct node* )malloc(sizeof(struct node));
+	printf("Enter data: ");
+	scanf("%d", &temp->data);
+	temp->next = NULL;
+
+	if (front == NULL)
+	{
+		front = rear = temp;
+		return;
+	}
+
+	rear->next = temp;
+	rear = temp;
+}
+
+void dequeue()
+{
+	if (front == NULL)
+	{
+		printf("Empty!\n");
+		return;
+	}
+	struct node* temp = front;
+	printf("data: %d\n", front->data);
+	if (front == rear)
+		front = rear = NULL;
+	else 
+		front = front->next;
+	free(temp);
+}
+
+void atFront()
+{
+	if (front == NULL)
+	{
+		printf("Empty!\n");
+		return;
+	}
+	printf("At the top: %d\n", front->data);
+}
+
+int main()
+{
+	int choice;
+
+	while(1)
+	{
+		printf("1. Enqueue\n2. Dequeue\n3. At front\n4. Exit\n\nEnter Choice: ");
+	scanf("%d", &choice);
+		switch(choice)
+		{
+			case 1: 
+				enqueue();
+				break;
+			case 2:
+				dequeue();
+				break;
+			case 3:
+				atFront();
+				break;
+			default:
+				exit(0);
+		}
+	}
+
+}