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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:

Flowchart: Check two numbers are Amicable numbers or not
Flowchart: Check two numbers are Amicable numbers or not

C++ Code Editor:

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Previous: Write a program in C++ to find Duck Numbers between 1 to 500.
Next: Write a program in C++ to count the Amicable pairs in an array.

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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