Question

IN C++

- [(1)] Design a Stack that is composed ONLY of one or two Queue objects ergo the ONLY instance variables that exist in this stack are queues. Stack class should contain the following methods: Print, Pop, Push, Top, Size, isEmpty, copy [(2)] Design a Queue that is composed ONLY of two Stacks objects ergo the ONLY instance variables that exist in this queue are stacks. Queue class should contain the following methods: Print, Enqueue, Dequeue, Front, Rear, Size, isEmpty, Copy

Answer 1

ANSWER :-

1) Program to implement a stack using two queue -

#include <iostream>

using namespace std;

class Stack {

    queue<int> q1, q2;

  int curr_size;

public:

    Stack()

    {

        curr_size = 0;

    }

void push(int x)

    {

       curr_size++;

// Push x first in empty q2

        q2.push(x);

// Push all the remaining

        // elements in q1 to q2.

        while (!q1.empty()) {

            q2.push(q1.front());

            q1.pop();

        }

        queue<int> q = q1;

        q1 = q2;

        q2 = q;

    }

void pop()

    {

// if no elements are there in q1

        if (q1.empty())

            return;

        q1.pop();

        curr_size--;

    }

int top()

    {

        if (q1.empty())

            return -1;

        return q1.front();

    }

   int size()

    {

        return curr_size;

    }

};

// Driver code

int main()

{

    Stack s;

    s.push(1);

    s.push(2);

    s.push(3);

    cout << "current size: " << s.size()

         << endl;

    cout << s.top() << endl;

    s.pop();

    cout << s.top() << endl;

    s.pop();

    cout << s.top() << endl;

cout << "current size: " << s.size()

         << endl;

    return 0;

}

2) program implement queue using two stack-

#include <iostream>

using namespace std;

class Queue {
public:
Stack S1, S2;
  
//declaring enqueue method
void enqueue(int x);
  
//declaring dequeue method
int dequeue();
};

// enqueue function
void Queue :: enqueue(int x)
{
S1.push(x);
cout << "Element Inserted into Queue\n";
}

// dequeue function
int Queue :: dequeue()
{
int x, y;
while(!S1.isEmpty())
{
// take an element out of first stack
x = S1.pop();
// insert it into the second stack
S2.push(x);
}
    
y = S2.pop();

while(!S2.isEmpty())
{
x = S2.pop();
S1.push(x);
}
  
return y;
}

// main function
int main()
{
Queue q;
q.enqueue(10);
q.enqueue(100);
q.enqueue(1000);
cout << "Removing element from queue" << q.dequeue();
  
return 0;
}