Stack and Queue as ADT in C++

Stack as ADT

The functions associated with stack are:
empty() – Returns whether the stack is empty

size() – Returns the size of the stack
top() – Returns a reference to the top most element of the stack
push(g) – Adds the element ‘g’ at the top of the stack
pop() – Deletes the top most element of the stack

Example:

#include <iostream>

#include <stack>

using namespace std;

void showstack(stack <int> s)

{

    while (!s.empty())

    {

        cout << '\t' << s.top();

        s.pop();

    }

    cout << '\n';

}

int main ()

{

    stack <int> s;

    s.push(10);

    s.push(30);

    s.push(20);

    s.push(5);

    s.push(1);

    cout << "The stack is : ";

    showstack(s);

    cout << "\ns.size() : " << s.size();

    cout << "\ns.top() : " << s.top();

    cout << "\ns.pop() : ";

    s.pop();

    showstack(s);

    return 0;

}

Output:

The stack is :       1      5      20     30     10

s.size() : 5

s.top() : 1

s.pop() :     5      20     30     10

Queue As ADT

The functions supported by queue are :

1.      empty() – Returns whether the queue is empty.

2.      size() – Returns the size of the queue.

3.      queue::swap() in C++ STL: Exchange the contents of two queues but the queues must be of same type, although sizes may differ.

4.      queue::emplace() in C++ STL: Insert a new element into the queue container, the new element is added to the end of the queue.

5.      queue::front() and queue::back() in C++ STL– front() function returns a reference to the first element of the queue. back() function returns a reference to the last element of the queue.

6.      push(g) and pop() – push() function adds the element ‘g’ at the end of the queue. pop() function deletes the first element of the queue.

#include <iostream>

#include <queue>

using namespace std;

void showq(queue <int> q1)

{

    while (!q1.empty())

    {

        cout << '\t' << q1.front();

        q1.pop();

    }

    cout << '\n';

}

int main()

{

    queue <int> q;

    q.push(10);

    q.push(20);

    q.push(30);

    cout << "The queue is : ";

    showq(q);

    cout << "\nsize() : " << q.size();

    cout << "\nfront() : " << q.front();

    cout << "\nback() : " << q.back();

    q.pop();

    cout << "\nThe queue after pop() : ";

    showq(q);

    return 0;

}

Output:

The queue is :       10     20     30

size() : 3

front() : 10

back() : 30

The queue after pop() :    20     30