#include <iostream>
using namespace std;

// Function to print divisors of a number excluding 1 and the number itself
void print_div(int number) {
    bool hasDivisors = false;  // Flag to check if any divisors were found
    for (int i = 2; i <= number / 2; i++) { // Start from 2 and go up to half of the number
        if (number % i == 0) {   // If `i` divides `number` evenly, it's a divisor
            cout << i << " ";
            hasDivisors = true;
        }
    }
    if (!hasDivisors) cout << "(empty)"; // Print (empty) if no divisors were found
    cout << endl;
}

// Function to calculate the sum of divisors of a number that are less than itself
int sum_div(int number) {
    int sum = 0;
    for (int i = 1; i < number; i++) { // Go through all numbers less than `number`
        if (number % i == 0) {          // If `i` is a divisor, add it to `sum`
            sum += i;
        }
    }
    return sum;
}

// Function to find and print perfect numbers from 1 to n
void print_perfect_numbers(int n) {
    for (int i = 1; i <= n; i++) {
        if (sum_div(i) == i) { // If the sum of divisors equals the number itself, it's perfect
            cout << i << " ";
        }
    }
    cout << endl;
}

int main() {
    int number = 12;
    cout << "Divisors of " << number << " (excluding 1 and itself): ";
    print_div(number);

    cout << "Sum of divisors of " << number << " (excluding itself): " << sum_div(number) << endl;

    int n = 30;
    cout << "Perfect numbers from 1 to " << n << ": ";
    print_perfect_numbers(n);

    return 0;
}

C++ Online Compiler

Write, Run & Share C++ code online using OneCompiler's C++ online compiler for free. It's one of the robust, feature-rich online compilers for C++ language, running on the latest version 17. Getting started with the OneCompiler's C++ compiler is simple and pretty fast. The editor shows sample boilerplate code when you choose language as C++ and start coding!

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
}