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CircularQueue.cpp
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CircularQueue.cpp
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#include <iostream>
using namespace std;
// a general template class of Queue implemented with circular arrays
template <typename type, const int max_size = 100>
class Queue
{
private:
public:
int front; // index of first element
int rear; // index of last element
type storage[max_size]{}; // the storage warehouse of elements
unsigned size; // the number of elements
// returns the next index from given index in the circular array
// RECEIVES: the index
// RETURNS: the next index in array
int inc(const int &it) const { return ((it 1) % max_size); }
// returns the previous index from given index in the circular array
// RECEIVES: the index
// RETURNS: the previous index in array
int dec(const int &it) const { return ((it - 1) % max_size); }
public:
// constructor:
Queue() : front(0), rear(-1), size(0) {}
// prints the contents of queue on console
// note: '<<' operator is used
// RECEIVES: nothing
// RETURNS: nothing
void display() const
{
// logical illustration:
if (empty()) // return if empty
return;
for (int i = front; i != rear; i = inc(i))
cout << storage[i] << " ";
cout << storage[rear] << " ";
// physical illustration:
// for (int i = 0; i < max_size; i )
// {
// if (i == front && i == rear)
// printf(" $");
// else if (i == front)
// printf(" ");
// else if (i == rear)
// printf(" -");
// else
// printf(" ");
// cout << storage[i] << " ";
// }
puts("");
}
// inserts a new element at the end of queue
// RECEIVES: data = the contents of new element
// RETURNS: the index of new element in queue
int enqueue(const type &data)
{
if (full()) // error if already full
throw "In enqueue() : queue is full";
rear = inc(rear);
storage[rear] = data;
size ;
return rear;
}
// removes an element from the front of queue
// RECEIVES: nothing
// RETURNS: the contents of removed element
type dequeue()
{
if (empty()) // error if already empty
throw "In dequeue() : queue is empty";
type ret;
ret = storage[front];
storage[front] = 0;
front = inc(front);
size--;
return ret;
}
// clears the queue completely
// RECEIVES: nothing
// RETURNS: nothing
void clear()
{
front = 0;
rear = -1;
size = 0;
}
// returns whether the queue is empty or not
// RECEIVES: nothing
// RETURNS: bool value
bool empty() const { return size == 0; }
// returns whether the queue is full or not
// RECEIVES: nothing
// RETURNS: bool value
bool full() const { return size == max_size; }
// returns the number of elements in queue
// RECEIVES: nothing
// RETURNS: numbre of elements
unsigned length() const { return size; }
// returns the contents of element at front
// RECEIVES: nothing
// RETURNS: the element
type begin() const { return storage[front]; }
// returns the contents of element at rear
// RECEIVES: nothing
// RETURNS: the element
type end() const { return storage[rear]; }
};
int main()
{
Queue<int, 10> q;
q.display();
for (int i = 1; i <= 5; i )
{
q.enqueue(i);
q.display();
}
for (int i = 1; i <= 4; i )
{
q.dequeue();
q.display();
}
for (int i = 1; i <= 9; i )
{
q.enqueue(i);
q.display();
}
for (int i = 1; i <= 10; i )
{
q.dequeue();
q.display();
}
q.enqueue(9);
q.display();
return 0;
}