#include<bits/stdc++.h>
using namespace std;

#define N 5

class deq{
  int a[N];
  int front,rear;
  
  public: 
   deq(){
     front=rear=-1;
   }
   
   void push_front(int val);
   void push_back(int val);
   void pop_front();
   void pop_back();
   void display();
};

void deq::push_back(int val){
  if(front==-1 && rear==-1){
    front=rear=0;
    a[rear]=val;
  } else if(((rear+1)%N)==front){
    cout<<"Deque is Full!!\n";
  } else {
    rear=(rear+1)%N;
    a[rear]=val;
  }
}

void deq::push_front(int val){
  if(front==-1 && rear==-1){
    front=rear=0;
    a[front]=val;
  } else if(((rear+1)%N)==front){
    cout<<"Deque is FULL!!\n";
  } else if(front==0){
    front=N-1;
    a[front]=val;
  } else {
    front--;
    a[front]=val;
  }
}

void deq::pop_back(){
  if(front==-1 && rear==-1){
    cout<<"Deque is empty\n";
  } else if(rear==0){
    rear=N-1;
  } else {
    rear--;
  }
}

void deq::pop_front(){
  if(front==-1 && rear==-1){
    cout<<"Deque is empty!!\n";
  } else if(front==N-1){
    front=0;
  } else {
    front++;
  }
}

void deq::display(){
  if(front==-1 && rear==-1){
    cout<<"Deque is empty!!\n";
  } else {
    int i=front;
    while(i!=rear){
      cout<<a[i]<<" ";
      i=(i+1)%N;
    }
    cout<<a[rear];
  }
}

int main(){
  deq dq;
  dq.push_back(1);
  dq.push_back(2);
  dq.push_back(3);
  dq.push_back(4);
  dq.push_front(5);
  dq.pop_back();
  dq.push_front(6);
  dq.pop_front();
  dq.display();
}
by

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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
}