﻿ C++ Exercises: Check if a number is Keith or not - w3resource

C++ Exercises: Check if a number is Keith or not

C++ Numbers: Exercise-40 with Solution

Write a program in C++ to check if a number is Keith or not.

Sample Solution:

C++ Code :

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

int lenCount(int nm)
{  int ctr=0;
while(nm>0)
{
nm=nm/10;
ctr++;
}
return ctr;
}

int main()
{
int num1=0,arr1[10],num2=0,flg=0,i=0,sum=0;
cout << "\n\n Check whether a number is Keith or not: \n";
cout <<" Sample Keith numbers: 197, 742, 1104, 1537, 2208, 2580, 3684, 4788, 7385..\n";
cout << " -----------------------------------------------------------------------\n";
cout<<" Input a number : ";
cin>>num1;
num2=num1;
for(i=lenCount(num2)-1;i>=0;i--)
{
arr1[i]=num1 % 10;
num1/=10;
}
while(flg==0)
{
for(i=0;i<lenCount(num2);i++)
sum+=arr1[i];
if(sum==num2)
{
cout<<" The given number is a Keith Number.\n";
flg=1;
}
if(sum>num2)
{
cout<<" The given number is not a Keith number.\n";
flg=1;
}
for(i=0;i<lenCount(num2);i++)
{
if(i!=lenCount(num2)-1)
arr1[i]=arr1[i+1];
else
arr1[i]=sum;
}
sum=0;
}
}
``````

Sample Output:

``` Check whether a number is Keith or not:
Sample Keith numbers: 197, 742, 1104, 1537, 2208, 2580, 3684, 4788, 7385..
-----------------------------------------------------------------------
Input a number : 742
The given number is a Keith Number.
```

Flowchart:

C++ Code Editor:

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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