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Implement a MyQueue class which implements a queue using two stacks : c++

9/7/2015

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/******************************************************************************************
*******************************************************************************************
Chapter 3 Stack and Queue

Implement a MyQueue class which implements a queue using two stacks.
We use two stacks, s1 and s2 for enqueue and dequeue. 
 
By: Hamed Kiani (Sep. 7, 2015)
******************************************************************************************
******************************************************************************************/

#include "stdafx.h"
#include <iostream>
using namespace std;

struct Node{
        int data;
        Node *next;
};

class MyQueue{
private:
        Node *_s1_head;     // enQueue is done using s1
        Node *_s2_head;     // s2 is used for dequeue
        int _s1_size;    // the size of s1 stack    
        int _s2_size;    // the size of s2 stack
        
public:
        MyQueue();
        ~MyQueue();
        void enQueue(int data);    // enqueue data value using s1
        Node* deQueue();             // dequeue using s1 and s2
        void print_s1();          // print elements of s1 stack
        void print_s2();          // print elements of s2 stack
        bool isEmpty(Node *); // check if s1 or s2 are empty
        int get_s1_size(){return _s1_size;}        // return size of s1
        int get_s2_size(){return _s2_size;}        // return size of s2
};

////////////////////////////////////////////////////////////////////
MyQueue::MyQueue()
{
        _s1_head = NULL;
        _s2_head = NULL; 
        _s1_size = 0;
        _s2_size = 0;
        cout << "the stack and queue are initialized! " << endl;
}

////////////////////////////////////////////////////////////////////
MyQueue::~MyQueue()
{
        Node *temp;
        
        while(_s1_head != NULL)
        {
                temp = _s1_head;
                _s1_head = _s1_head->next;
                delete temp;
        }

        while(_s2_head != NULL)
        {
                temp = _s2_head;            
                _s2_head = _s2_head->next;
                delete temp;
        }
        cout << "the stack and queue are deleted! " << endl;
}

////////////////////////////////////////////////////////////////////
// enQueue data at begin of s1 (push s1 stack)
void MyQueue::enQueue(int data)
{
        Node *temp = new Node;
        temp->data = data;
        temp->next = _s1_head;
        _s1_head = temp;
        _s1_size++;  
        cout << " the enQueue value is: " << data << endl;
}

////////////////////////////////////////////////////////////////////
// For deQueue, 
// we copy all from s1 to ss except the last node of s1 O(n)
// re-copy s2 to s1 in reverse order O(n)
// update the s1_size and s2_size
Node* MyQueue::deQueue()
{
        // the queue is empty and dequeue is not possible
        if ((_s1_size == 0) )
        {
                cout<< "dequeue is not possible !" << endl;
                return NULL;                 
        }

        // there is just one element in queue
        if ((_s1_size == 1) )
        {
                Node * temp = _s1_head;
                _s1_head = NULL;
                _s1_size--;
                cout << " the dequeue value is: " << temp->data << endl;
                return temp;
        }

        // there are more than one element in the queue
        _s2_head = _s1_head;
        _s1_head = NULL;
        Node * temp;
        temp = _s2_head;
        _s1_size--;
        while(temp->next->next != NULL)
        {
                temp = temp->next;
        }
        Node * temp2;
        temp2 = temp->next;
        temp->next = NULL;       
        _s1_head = _s2_head;
        _s2_head = NULL;
        cout << " the dequeue value is: " << temp2->data << endl;
        return temp2;
}

////////////////////////////////////////////////////////////////////
void MyQueue::print_s1()
{
        if (_s1_head == NULL)
        {
                cout << " stack s1 is empty" << endl;
                return;
        }
        Node* temp;
        temp = _s1_head;
        while(temp)
        {
                cout << temp->data << " " ;
                temp = temp->next;
        }
        cout << endl;
}

//////////////////////////////////////////////////////////
void MyQueue::print_s2()
{
        if (_s2_head == NULL)
        {
                cout << " stack s2 is empty" << endl;
                return;
        }
        Node* temp;
        temp = _s2_head;
        while(temp)
        {
                cout << temp->data << " " ;
                temp = temp->next;
        }
        cout << endl;
}
////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////

int _tmain(int argc, _TCHAR* argv[])
{
        MyQueue queue;
        queue.enQueue(1);        
        cout << queue.get_s1_size() << endl;
        cout << queue.get_s2_size() << endl;
        queue.print_s1();
        queue.print_s2();
        Node * temp = queue.deQueue();
        temp = queue.deQueue();
        temp = queue.deQueue();
        temp = queue.deQueue();
        temp = queue.deQueue();
        queue.print_s1();
        queue.print_s2();
        queue.enQueue(3);
        queue.enQueue(4);
        queue.print_s1();
        queue.print_s2();
        return 0;
}
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