﻿ C++ Exercises: Check two numbers are Amicable numbers or not - w3resource

# C++ Exercises: Check two numbers are Amicable numbers or not

## C++ Numbers: Exercise-28 with Solution

Write a program in C++ to check two numbers are Amicable numbers or not.

Sample Solution:

C++ Code :

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

int ProDivSum(int n)
{
int sum = 1;
for (int i=2; i<=sqrt(n); i++)
{
if (n%i == 0)
{
sum += i;
if (n/i != i)
sum += n/i;
}
}
return sum;
}
bool chkAmicable(int a,int b)
{
return(ProDivSum(a) == b && ProDivSum(b) == a);
}
int main()
{
int n, i, j, ctr,nm1,nm2;
cout << "\n\n Check whether two numbers are Amicable pairs or not: \n";
cout << "\n Sample: (220, 284), (1184, 1210), (2620, 2924).. \n";
cout << " --------------------------------------------------------\n";
cout<<" Input the 1st number : ";
cin>>nm1;
cout<<" Input the 2nd number : ";
cin>>nm2;

if( chkAmicable(nm1,nm2))
cout << " The given numbers are an Amicable pair."<<endl;
else
cout << " The given numbers are not an Amicable pair."<<endl;
return 0;
}
``````

Sample Output:

```Check whether two numbers are Amicable pairs or not:

Sample: (220, 284), (1184, 1210), (2620, 2924)..
--------------------------------------------------------
Input the 1st number : 220
Input the 2nd number : 284
The given numbers are an Amicable pair.
```

Flowchart:

C++ Code Editor:

What is the difficulty level of this exercise?

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## C++ Programming: Tips of the Day

How to use the PI constant in C++?

On some (especially older) platforms (see the comments below) you might need to

#define _USE_MATH_DEFINES and then include the necessary header file:
`#include<math.h>`

and the value of pi can be accessed via:

`M_PI`

In math.h (2014) it is defined as:

`# define M_PI           3.14159265358979323846  /* pi */`

but check your math.h for more. An extract from the "old" math.h (in 2009):

```/* Define _USE_MATH_DEFINES before including math.h to expose these macro
* definitions for common math constants.  These are placed under an #ifdef
* since these commonly-defined names are not part of the C/C++ standards.
*/```

However:

1. on newer platforms (at least on my 64 bit Ubuntu 14.04) I do not need to define the _USE_MATH_DEFINES
2. On (recent) Linux platforms there are long double values too provided as a GNU Extension:
`# define M_PIl          3.14159265358979323846`

Ref: https://bit.ly/3G4BgzQ