Queue.c

Queue.c

@@ -0,0 +1,101 @@
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+// A structure to represent a queue
+struct Queue {
+    int front, rear, size;
+    unsigned capacity;
+    int* array;
+};
+
+// function to create a queue
+// of given capacity.
+// It initializes size of queue as 0
+struct Queue* createQueue(unsigned capacity)
+{
+    struct Queue* queue = (struct Queue*)malloc(
+        sizeof(struct Queue));
+    queue->capacity = capacity;
+    queue->front = queue->size = 0;
+
+    // This is important, see the enqueue
+    queue->rear = capacity - 1;
+    queue->array = (int*)malloc(
+        queue->capacity * sizeof(int));
+    return queue;
+}
+
+// Queue is full when size becomes
+// equal to the capacity
+int isFull(struct Queue* queue)
+{
+    return (queue->size == queue->capacity);
+}
+
+// Queue is empty when size is 0
+int isEmpty(struct Queue* queue)
+{
+    return (queue->size == 0);
+}
+
+// Function to add an item to the queue.
+// It changes rear and size
+void enqueue(struct Queue* queue, int item)
+{
+    if (isFull(queue))
+        return;
+    queue->rear = (queue->rear + 1)
+                  % queue->capacity;
+    queue->array[queue->rear] = item;
+    queue->size = queue->size + 1;
+    printf("%d enqueued to queue\n", item);
+}
+
+// Function to remove an item from queue.
+// It changes front and size
+int dequeue(struct Queue* queue)
+{
+    if (isEmpty(queue))
+        return INT_MIN;
+    int item = queue->array[queue->front];
+    queue->front = (queue->front + 1)
+                   % queue->capacity;
+    queue->size = queue->size - 1;
+    return item;
+}
+
+// Function to get front of queue
+int front(struct Queue* queue)
+{
+    if (isEmpty(queue))
+        return INT_MIN;
+    return queue->array[queue->front];
+}
+
+// Function to get rear of queue
+int rear(struct Queue* queue)
+{
+    if (isEmpty(queue))
+        return INT_MIN;
+    return queue->array[queue->rear];
+}
+
+// Driver program to test above functions./
+int main()
+{
+    struct Queue* queue = createQueue(1000);
+
+    enqueue(queue, 10);
+    enqueue(queue, 20);
+    enqueue(queue, 30);
+    enqueue(queue, 40);
+
+    printf("%d dequeued from queue\n\n",
+           dequeue(queue));
+
+    printf("Front item is %d\n", front(queue));
+    printf("Rear item is %d\n", rear(queue));
+
+    return 0;
+}