#include<iostream>

using namespace std;

class Queue {
  private:
    int front;
  int rear;
  int arr[5];

  public:
    Queue() {
      front = -1;
      rear = -1;
      for (int i = 0; i < 5; i++) {
        arr[i] = 0;
      }
    }
  bool isEmpty() {
    if (front == -1 && rear == -1)
      return true;
    else
      return false;
  }
  bool isFull() {
    if (rear == 4)
      return true;
    else
      return false;
  }
  void enqueue(int val) {
    if (isFull()) {
      cout << "Queue full" << endl;
      return;
    } else if (isEmpty()) {
      rear = 0;
      front = 0;
      arr[rear] = val;
    } else {
      rear++;
      arr[rear] = val;
    }

  }

  int dequeue() {
    int x = 0;
    if (isEmpty()) {
      cout << "Queue is Empty" << endl;
      return x;
    } else if (rear == front) {
      x = arr[rear];
      rear = -1;
      front = -1;
      return x;
    } else {
      cout << "front value: " << front << endl;
      x = arr[front];
      arr[front] = 0;
      front++;
      return x;
    }
  }

  int count() {
    return (rear - front + 1);
  }

  void display() {
    cout << "All values in the Queue are - " << endl;
    for (int i = 0; i < 5; i++) {
      cout << arr[i] << "  ";
    }
  }

};

int main() {
  Queue q1;
  int value, option;

  do {
    cout << "\n\nWhat operation do you want to perform? Select Option number. Enter 0 to exit." << endl;
    cout << "1. Enqueue()" << endl;
    cout << "2. Dequeue()" << endl;
    cout << "3. isEmpty()" << endl;
    cout << "4. isFull()" << endl;
    cout << "5. count()" << endl;
    cout << "6. display()" << endl;
    cout << "7. Clear Screen" << endl << endl;

    cin >> option;

    switch (option) {
    case 0:
      break;
    case 1:
      cout << "Enqueue Operation \nEnter an item to Enqueue in the Queue" << endl;
      cin >> value;
      q1.enqueue(value);
      break;
    case 2:
      cout << "Dequeue Operation \nDequeued Value : " << q1.dequeue() << endl;
      break;
    case 3:
      if (q1.isEmpty())
        cout << "Queue is Empty" << endl;
      else
        cout << "Queue is not Empty" << endl;
      break;
    case 4:
      if (q1.isFull())
        cout << "Queue is Full" << endl;
      else
        cout << "Queue is not Full" << endl;
      break;
    case 5:
      cout << "Count Operation \nCount of items in Queue : " << q1.count() << endl;
      break;
    case 6:
      cout << "Display Function Called - " << endl;
      q1.display();
      break;
    case 7:
      system("cls");
      break;
    default:
      cout << "Enter Proper Option number " << endl;
    }

  } while (option != 0);

  return 0;
}
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Read inputs from stdin

OneCompiler's C++ online compiler supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample program which takes name as input and print your name with hello.

#include <iostream>
#include <string>
using namespace std;

int main() 
{
    string name;
    cout << "Enter name:";
    getline (cin, name);
    cout << "Hello " << name;
    return 0;
}

About C++

C++ is a widely used middle-level programming language.

  • Supports different platforms like Windows, various Linux flavours, MacOS etc
  • C++ supports OOPS concepts like Inheritance, Polymorphism, Encapsulation and Abstraction.
  • Case-sensitive
  • C++ is a compiler based language
  • C++ supports structured programming language
  • C++ provides alot of inbuilt functions and also supports dynamic memory allocation.
  • Like C, C++ also allows you to play with memory using Pointers.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition If-Else is used.

if(conditional-expression) {
   //code
}
else {
   //code
}

You can also use if-else for nested Ifs and If-Else-If ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to If-Else-If ladder.

switch(conditional-expression){    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
......    
    
default:     
 code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  //code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while (condition) {  
// code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {  
 // code 
} while (condition);

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity. Function gets run only when it is called.

How to declare a Function:

return_type function_name(parameters);

How to call a Function:

function_name (parameters)

How to define a Function:

return_type function_name(parameters) {  
 // code
}