PUSH POP OPERATION USING C++

ARRAY REPRESENTATION OF STACK:- 

(LIFO- LAST IN FIRST OUT)

EXAMPLE:

Initially:

empty stack

top = -1

step 1: push 3

           top ++

step 2: push 5

           top++

step 3,4: push 7,9

              top + +

step 5: push 2

          stack overflow

step 6: pop

            top--

step 7,8,9: pop

                 top--

step 10: pop

             stack underflow

        

 PUSH OPERATION:

step 1: start

step 2: if (top=length-1)

            then

                print("stack overflow")

                return 

           endif

step 3: top=top+1

step 4: read n

step 5: arr[top]=n

step 6: stop

 POP OPERATION:

step 1: start

step 2: if top =-1

           then

                print("stack underflow")

                return

          endif

step 3: n=arr[top]

step 4: print n 

step 5: top=top-1

step 6: stop

  PROGRAM:

#include <iostream>
using namespace std;

#define max 30
class stack
{
    int a[max], top;

    public:
    stack()
    {
        top = -1;
    }

    void push(int n)
    {
        if(top == max-1)
        {
            cout<<"stack overflow"<<endl;
            return;
        }
        top++;
        a[top]=n;
    }

    void pop()
    {
        if(top==-1)
        {
            cout<<"stack underflow"<<endl;
            return;
        }
        int n=a[top];
        cout<<"popped element"<<a[top]<<endl;
        top--;
    }
    void display()
    {
        if(top == -1)
        {
            cout<<"empty stack"<<endl;
        }
        else
        {
            for(int i=top;i>=0;i--)
            {
                cout<<a[i]<<endl;
            }
        }
    }

    void peep()
    {
        if(top == -1)
        {
            cout<<"empty stack"<<endl;
        }
        else
        {
            cout<<a[top]<<endl;
        }
    }
};

int main()
{
    stack ob;
    while(1)
    {
        cout<<"enter 1 for push"<<endl;
        cout<<"enter 2 for pop"<<endl;
        cout<<"enter 3 for display"<<endl;
        cout<<"enter 4 for peep"<<endl;
        cout<<"enter 5 for exit"<<endl;

        int choice;
        cin>>choice;

        switch (choice)
        {
        case 1:
            cout<<"enter a value for push operation"<<endl;

             int n;

             cin>>n;

             ob.push(n);
            break;
        case 2:
            ob.pop();
            break;
        case 3:
            ob.display();
            break;
        case 4:
            ob.peep();
            break;
        case 5:
            cout<<"end of program"<<endl;
            break;
        default:
            cout<<"invalid option"<<endl;
        }
        if(choice==5)
        break;
    }
}

Thread class in Java - 6

 6. Priority

class ThreadPrio implements Runnable

{

Thread t;

ThreadPrio()

{

t=new Thread(this,"hello thread");

System.out.println(t);

t.start();

}

public void run()

{

System.out.println("hello thread started---");

try

{

Thread.sleep(1000);

}

catch(InterruptedException e)

{

}

System.out.println(t);

}

}

class T6Demo

{

public static void main(String args[])

{

ThreadPrio ob1=new ThreadPrio();

System.out.println("main thread "+Thread.currentThread());

ob1.t.setPriority(4);

}

}

o/p:------------------------------------------------------------------------------------------

ddmc@ddmc-desktop:~$ java T6Demo

Thread[hello thread,5,main]

hello thread started---

main thread Thread[main,5,main]

Thread[hello thread,4,main]

Thread class in Java - 5

 5. isAlive() and join()

class CreateOne implements Runnable

{

String name;

Thread t;

CreateOne(String s)

{

name=s;

t=new Thread(this,name);

System.out.println("First thread "+t);

t.start();

}

public void run()

{

try

{

for(int i=0;i<5;i++)

{

System.out.println(name+" : "+i);

Thread.sleep(1000);

}

}

catch(InterruptedException e)

{

System.out.println("caught");

}

System.out.println(name + "exiting");

}

}

class CreateTwo implements Runnable

{

String name;

Thread t;

CreateTwo(String s)

{

name=s;

t=new Thread(this,name);

System.out.println("First thread "+t);

t.start();

}

public void run()

{

try

{

for(int i=0;i<5;i++)

{

System.out.println(name+" : "+i);

Thread.sleep(500);

}

}

catch(InterruptedException e)

{

System.out.println("caught");

}

System.out.println(name + "exiting");

}

}

class T5Demo

{

public static void main(String args[])

{

CreateOne ob1=new CreateOne("One");

CreateTwo ob2=new CreateTwo("Two");

System.out.println("First thread is alive or not ---"+ob1.t.isAlive());

System.out.println("Second thread is alive or not ---"+ob2.t.isAlive());

//wait for the threads to finish

try

{

ob1.t.join();

ob2.t.join();

}

catch(InterruptedException e)

{

}

System.out.println("First thread is alive or not ---"+ob1.t.isAlive());

System.out.println("Second thread is alive or not ---"+ob2.t.isAlive());

System.out.println("exiting main");

}

}

o/p:-------------------------------------------------------------

ddmc@ddmc-desktop:~$ java T5Demo

First thread Thread[One,5,main]

First thread Thread[Two,5,main]

First thread is alive or not ---true

Second thread is alive or not ---true

One : 0

Two : 0

Two : 1

One : 1

Two : 2

Two : 3

One : 2

Two : 4

Twoexiting

One : 3

One : 4

Oneexiting

First thread is alive or not ---false

Second thread is alive or not ---false

exiting main

Thread class in Java - 4

 4. Creating multiple threads

class Multi implements Runnable

{

String name;

Thread t;

Multi(String s)

{

name=s;

t=new Thread(this,name);

System.out.println("new thread "+t);

t.start();

}

public void run()

{

try

{

for(int i=5;i>0;i--)

{

System.out.println(name+" : "+i);

Thread.sleep(1000);

}

}

catch(InterruptedException e)

{

System.out.println(name + "interrupted");

}

System.out.println(name + "exiting");

}

}

class T4Demo

{

public static void main(String args[])

{

new Multi("one");

new Multi("two");

new Multi("three");

try

{

//wait for the other thread

Thread.sleep(10000);

}

catch(InterruptedException e)

{

System.out.println("main thread interrupted ");

}

System.out.println("exiting main thread ");

}

}

o/p:------------------------------------------------------------------------------

class Multi implements Runnable

{

String name;

Thread t;

Multi(String s)

{

name=s;

t=new Thread(this,name);

System.out.println("new thread "+t);

t.start();

}

public void run()

{

try

{

for(int i=5;i>0;i--)

{

System.out.println(name+" : "+i);

Thread.sleep(1000);

}

}

catch(InterruptedException e)

{

System.out.println(name + "interrupted");

}

System.out.println(name + "exiting");

}

}

class T4Demo

{

public static void main(String args[])

{

new Multi("one");

new Multi("two");

new Multi("three");

try

{

//wait for the other thread

Thread.sleep(10000);

}

catch(InterruptedException e)

{

System.out.println("main thread interrupted ");

}

System.out.println("exiting main thread ");

}

}

o/p: ---------------- -----------------------------------

ddmc@ddmc-desktop:~$ java T4Demo

new thread Thread[one,5,main]

new thread Thread[two,5,main]

new thread Thread[three,5,main]

one : 5

two : 5

three : 5

one : 4

three : 4

two : 4

one : 3

three : 3

two : 3

one : 2

three : 2

two : 2

one : 1

three : 1

two : 1

threeexiting

twoexiting

oneexiting

exiting main thread

Thread class in Java - 3

 3. Creating thread by extending Thread class

class MyNewThread extends Thread

{

MyNewThread()

{

//creating new thread

super("Demo thread");

System.out.println("child thread "+this);

start();

}

public void run()

{

try

{

for(int i=0;i<5;i++)

{

System.out.println("child thread "+i);

Thread.sleep(500);

}

}

catch(InterruptedException e)

{

System.out.println("child interrupted ");

}

System.out.println("exiting child thread----");

}

}

class T3Demo

{

public static void main(String args[])

{

new MyNewThread();

try

{

for(int i=90;i<95;i++)

{

System.out.println("main thread "+i);

Thread.sleep(1000);

}

}

catch(InterruptedException e)

{

System.out.println("main interrupted ");

}

System.out.println("exiting main thread----");

}

}

o/p:--------------------------------------------------------------------------------------------------

ddmc@ddmc-desktop:~$ java T3Demo

child thread Thread[Demo thread,5,main]

child thread 0

main thread 90

child thread 1

child thread 2

main thread 91

child thread 3

child thread 4

main thread 92

exiting child thread----

main thread 93

main thread 94

exiting main thread----

Thread class in Java - 1

 Java Thread Programs

1. Dealing with main

class T1Demo

{

public static void main(String args[])

{

Thread t=Thread.currentThread();

System.out.println("current "+t);

System.out.println(t.getName());

t.setName("MyMain");

System.out.println("current now "+t);

System.out.println(t.getName());

try

{

for(int i=0;i<10;i++)

{

System.out.println(i);

Thread.sleep(1000);

}

}

catch(InterruptedException e)

{

System.out.println("caught");

}

}

}

o/p: --------------------------------------------------------------------------------------------

ddmc@ddmc-desktop:~$ java T1Demo

current Thread[main,5,main]

main

current now Thread[MyMain,5,main]

MyMain

0

1

2

3

4

5

6

7

8

9

In [main, 5, main], 5 is the priority of the thread, the last main is the group name of the thread.

Thread class in Java - 2

 2. Creating new thread by implementing Runnable

class NewThread implements Runnable

{

Thread t;

NewThread()

{

//create a new thread

t=new Thread(this,"Demo Thread");

System.out.println("child thread "+t);

t.start();

}

public void run()

{

try

{

for(int i=5;i>0;i--)

{

System.out.println("child "+i);

Thread.sleep(500);

}

}

catch(InterruptedException e)

{

System.out.println("child interrupted");

}

System.out.println("exiting child thread");

}

}

class T2Demo

{

public static void main(String args[])

{

new NewThread();

try

{

for(int i=100;i>95;i--)

{

System.out.println("Main "+i);

Thread.sleep(1000);

}

}

catch(InterruptedException e)

{

System.out.println("main interrupted");

}

System.out.println("exiting main thread");

}

}

o/p: -------------------------------------------------------------------------------------------

ddmc@ddmc-desktop:~$ java T2Demo

child thread Thread[Demo Thread,5,main]

child 5

Main 100

child 4

Main 99

child 3

child 2

Main 98

child 1

exiting child thread

Main 97

Main 96

exiting main thread

--------------------------------------------------------------------------------------------------