Day_133.cpp

//  **** DAY 133 - Introduction to STACK *****

/*


// Implementation of stack using arrays
#include<iostream>
using namespace std;

class stack
{
    int *arr;
    int size , top;

    public:
    // constructor
    stack(int val)
    {
        arr = new int[val];
        size = val;
        top = -1;
    }

    // push function to insert elements iside the stack
    void push(int data)
    {
        // check stack is full or not
        if(top == size-1)
        {
            cout<<" Stack overflow "<<endl;
        }
        else
        {
            cout<<data<<" is pushed into stack "<<endl;
            top++;
            arr[top] = data;
        }
    }

    // pop function to deletion element from stack
    void pop()
    {
        // check stack is empty or not
        if(top == -1)
        {
            cout<<" Stack underflow "<<endl;
        }
        else
        {
            cout<<arr[top]<<" is popped from stack "<<endl;
            top--;
        }
    }

// to find peak element
    int peak()
    {
        if(top == -1)
        {
            cout<<" Stack is empty "<<endl;
            return -1;
        }
        else
        return arr[top];
    }
    // isEmpty function return 1 - if stack is empty else it returns 0
    bool isEmpty()
    {
        return top==-1;
    }

    // Actual size of an stack
    int Asize()
    {
        return top+1;
    }

};

int main()
{

    stack s(5);
    s.push(3);
    s.push(4);
    s.push(6);

      cout<<"Size "<<s.Asize()<<endl;
    s.pop();
    s.pop();
    s.pop();

  cout<<" Isempty : "<<s.isEmpty()<<endl;
 s.push(6);
  int value =s.peak();
  if(s.isEmpty() == 0)
  {
     cout<<value<<endl;
  }



    return 0;
}

*/

/*

// Implementation of stack using Linked List

#include<iostream>
using namespace std;

// singly linked list implementation
class Node
{
    public:
    int data;
    Node *next;

    // constructor
    Node(int d)
    {
        data = d;
        next = NULL;
    }
};

class stack
{

    Node *top;
    int size; // actual size

    public:
    // constructor
    stack()
    {
        top= NULL;
        size=0;
    }

    // push function
    void push(int x1)
    {
        Node *temp = new Node(x1);
        if(temp == NULL)
        {
            cout<<"Stack overflow "<<endl;
            return ;
        }
        else
        {
            temp->next = top;
            top = temp;
            size++;
            cout<<"Pushed "<<x1<<" into stack\n";
        }
    }

    // Pop function
    void pop()
    {
        if(top == NULL)
        {
            cout<<"Stack underflow"<<endl;
            return;
        }
        else
        {
            cout<<top->data<<" popped from stack\n";
            Node *temp = top;
            top = top->next;
            delete temp;
            size--;
        }
    }

    // to get peak element
    int peak()
    {
        if(top == NULL)
        {
            cout<<"Stack is empty \n";
            return -1;
        }
        else
        {
            return top->data;
        }
    }

    // Actual size of stack
    int Asize()
    {
        return size;
    }

    // check empty or not
    bool isEmpty()
    {
        return top==NULL;
    }
};


int main()
{
    stack s;
    s.push(12);
    s.push(24);
    s.push(123);

      cout<<"Size "<<s.Asize()<<endl;
    s.pop();
    s.pop();

      cout<<" Isempty : "<<s.isEmpty()<<endl;
 s.push(6);
  int value =s.peak();

    if(s.isEmpty() == 0)
  {
     cout<<value<<endl;
  }
    return 0;
}

*/

// Implementation if STACK USing STL(Standard Templet Library)

#include <iostream>
#include <stack>
// stack library included
using namespace std;

int main()
{

    // creating an s named stack
    stack<int> s;

    s.push(12);
    s.push(24);
    s.push(123);

    // size of the stack
    cout << "Size " << s.size() << endl;
    s.pop();
    s.pop();

    cout << " Isempty : " << s.empty() << endl;
    s.push(6);

    //  to get peak element
    int value = s.top();

    if (s.empty() == 0)
    {
        cout << value << endl;
    }

    return 0;
}