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C++ Exercises: Create the first twenty Hamming numbers

C++ Numbers: Exercise-42 with Solution

Write a program in C++ to create the first twenty Hamming numbers.

Sample Solution:

C++ Code:

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

bool chkHhamming (int n) 
{
	if (n == 1) return true;
	if (n%2==0 or n%3==0 or n%5==0) 
	{
		for (int i = 2; i*i < n; ++i) 
		{
			if (n%i == 0) {
				if (i%2 != 0 and i%3!=0 and 

i%5!=0) return false;
			}
			if (n%(n/i) == 0) {
				if ((n/i)%2 != 0 and (n/i)%3!=0 

and (n/i)%5!=0) return false;
			}
		}
		return true;		
	}
	return false;
}

int main () 
{
	int n,j;
	cout << "\n\n Find first twenty Hamming numbers: \n";
	cout << " ---------------------------------------\n";
	cout << " Input the upper limit of Hamming numbers: ";
	cin>>n;
	cout << " The Hamming numbers are: "<<endl;	
	
	while (j<=n) 
	{
		int count = 0;
		int i = 1;
		bool first = true;
		while (count < n) 
		{
			if (chkHhamming(i)) 
			{
				if (not first) cout << ",";
				cout << i;
				++count;
				first = false;
			}
			++i;
		}
		j++;
	}
	cout <<endl;
}

Sample Output:

 Find first twenty Hamming numbers:                                    
 ---------------------------------------                               
 Input the upper limit of Hamming numbers: 20                          
 The Hamming numbers are:                                              
1,2,3,4,5,6,8,9,10,12,15,16,18,20,24,25,27,30,32,361,2,3,4,5,6,8,9,10,1
2,15,16,18,20,24,25,27,30,32,361,2,3,4,5,6,8,9,10,12,15,16,18,20,24,25,
27,30,32,361,2,3,4,5,6,8,9,10,12,15,16,18,20,24,25,27,30,32,361,2,3,4,5
,6,8,9,10,12,15,16,18,20,24,25,27,30,32,361,2,3,4,5,6,8,9,10,12,15,16,1
8,20,24,25,27,30,32,361,2,3,4,5,6,8,9,10,12,15,16,18,20,24,25,27,30,32,
361,2,3,4,5,6,8,9,10,12,15,16,18,20,24,25,27,30,32,361,2,3,4,5,6,8,9,10
,12,15,16,18,20,24,25,27,30,32,361,2,3,4,5,6,8,9,10,12,15,16,18,20,24,2
5,27,30,32,361,2,3,4,5,6,8,9,10,12,15,16,18,20,24,25,27,30,32,361,2,3,4
,5,6,8,9,10,12,15,16,18,20,24,25,27,30,32,361,2,3,4,5,6,8,9,10,12,15,16
,18,20,24,25,27,30,32,361,2,3,4,5,6,8,9,10,12,15,16,18,20,24,25,27,30,3
2,361,2,3,4,5,6,8,9,10,12,15,16,18,20,24,25,27,30,32,361,2,3,4,5,6,8,9,
10,12,15,16,18,20,24,25,27,30,32,361,2,3,4,5,6,8,9,10,12,15,16,18,20,24
,25,27,30,32,361,2,3,4,5,6,8,9,10,12,15,16,18,20,24,25,27,30,32,361,2,3
,4,5,6,8,9,10,12,15,16,18,20,24,25,27,30,32,361,2,3,4,5,6,8,9,10,12,15,
16,18,20,24,25,27,30,32,361,2,3,4,5,6,8,9,10,12,15,16,18,20,24,25,27,30
,32,36

Flowchart:

Flowchart: Create the first twenty Hamming numbers

C++ Code Editor:

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Next: Write a C++ program to check whether a given number is an Armstrong number or not.

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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