// Queue.java: simple circular queue of chars
public class Queue {
   private int QSIZE = 4;
   private int q[] = new int[QSIZE];
   private int head = 0;
   private int tail = 0;
   private int size = 0;

   public void enqueue(int x) {
      if (!isFull()) {
         size++;
         q[tail] = x;
         if (tail == QSIZE - 1) tail = 0;
         else tail++;
      }
      else System.out.println("Overflow");
   }

   public int dequeue() {
      if (isEmpty()) {
         System.out.println("Underflow");
         return -1;
      }
      size--;
      int x = q[head];
      if (head == QSIZE - 1) head = 0;
      else head++;
      return x;
   }

   public boolean isEmpty() {
      return size == 0;
   }

   public boolean isFull() {
      return size == QSIZE;
   }

   public int getSize() {
      return size;
   }

   public int getFront() {
      if (!isEmpty())
         return q[head];
      else return -1;
   }

   public void dumpQ(int n) {
      System.out.println("n:" + n +
        ", size:" + size + ", head:" +
        head + ", tail:" + tail +
         ", frontitem:" + getFront());
   }

   public static void main(String[] args) {
      Queue queue = new Queue();
      queue.dumpQ(1);
      queue.enqueue(101);queue.dumpQ(2);
      queue.enqueue(202);queue.dumpQ(2);
      queue.enqueue(303);queue.dumpQ(2);
      System.out.println(queue.dequeue());
         queue.dumpQ(3);
      System.out.println(queue.dequeue());
         queue.dumpQ(3);
      System.out.println(queue.dequeue());
         queue.dumpQ(4);
      System.out.println(queue.dequeue());
         queue.dumpQ(4);
      queue.dumpQ(5);
      queue.enqueue(444);queue.dumpQ(6);
      queue.enqueue(555);queue.dumpQ(7);
      queue.enqueue(666);queue.dumpQ(8);
      queue.enqueue(777);queue.dumpQ(9);
      queue.enqueue(888);queue.dumpQ(10);
      System.out.println(queue.dequeue());
         queue.dumpQ(11);
      System.out.println(queue.dequeue());
         queue.dumpQ(12);
      System.out.println(queue.dequeue());
         queue.dumpQ(13);
      System.out.println(queue.dequeue());
         queue.dumpQ(14);
      System.out.println(queue.dequeue());
         queue.dumpQ(15);
   }
}

// queue.h: header file
int dequeue();
void enqueue(int );
int isempty();
int isfull();
int getfront();
void dumpq();
// queue.c: queue definition
#include <stdio.h>
#include "queue.h"
#define QSIZE 4

int q[QSIZE];
int head = 0;
int tail = 0;
int size = 0;

void enqueue(int x) {
   if (!isfull()) {
      size++;
      q[tail] = x;
      if (tail == QSIZE - 1) tail = 0;
      else tail++;
   }
   else printf("Overflow\n");
}
   
int dequeue() {
   int x;
   if (isempty()) {
      printf("Underflow\n");
      return -1;
   }
   size--;
   x = q[head];
   if (head == QSIZE - 1) head = 0;
   else head++;
   return x;
}
   
int isempty() {
   return size == 0;
}

int isfull() {
   return size == QSIZE;
}

int getfront() {
   if (!isempty())
      return q[head];
   else return -1;
}

void dumpq(int n) {
   printf("n:%i, size:%i, head:%i,\
      tail:%i, frontitem:%i\n", 
      n, size, head, tail, getfront());
}
// queuemain.c: test queue
#include <stdio.h>
#include "queue.h"

int main() {
   dumpq(1);
   enqueue(101);dumpq(2);
   enqueue(202);dumpq(2);
   enqueue(303);dumpq(2);
   printf("%i\n", dequeue());dumpq(3);
   printf("%i\n", dequeue());dumpq(3);
   printf("%i\n", dequeue());dumpq(4);
   printf("%i\n", dequeue());dumpq(4);
   dumpq(5);
   enqueue(444);dumpq(6);
   enqueue(555);dumpq(7);
   enqueue(666);dumpq(8);
   enqueue(777);dumpq(9);
   enqueue(888);dumpq(10);
   printf("%i\n", dequeue());dumpq(11);
   printf("%i\n", dequeue());dumpq(12);
   printf("%i\n", dequeue());dumpq(13);
   printf("%i\n", dequeue());dumpq(14);
   printf("%i\n", dequeue());dumpq(15);
}

n:1, size:0, head:0, tail:0, frontitem:-1
n:2, size:1, head:0, tail:1, frontitem:101
n:2, size:2, head:0, tail:2, frontitem:101
n:2, size:3, head:0, tail:3, frontitem:101
101
n:3, size:2, head:1, tail:3, frontitem:202
202
n:3, size:1, head:2, tail:3, frontitem:303
303
n:4, size:0, head:3, tail:3, frontitem:-1
Underflow
-1
n:4, size:0, head:3, tail:3, frontitem:-1
n:5, size:0, head:3, tail:3, frontitem:-1
n:6, size:1, head:3, tail:0, frontitem:444
n:7, size:2, head:3, tail:1, frontitem:444
n:8, size:3, head:3, tail:2, frontitem:444
n:9, size:4, head:3, tail:3, frontitem:444
Overflow
n:10, size:4, head:3, tail:3, frontitem:444
444
n:11, size:3, head:0, tail:3, frontitem:555
555
n:12, size:2, head:1, tail:3, frontitem:666
666
n:13, size:1, head:2, tail:3, frontitem:777
777
n:14, size:0, head:3, tail:3, frontitem:-1
Underflow
-1
n:15, size:0, head:3, tail:3, frontitem:-1