TheAlgorithms-C-Plus-Plus/Others/Happy_number.cpp

/* A happy number is a number whose sum of digits is calculated until the sum is a single digit,
  and this sum turns out to be 1 */
#include <iostream>
using namespace std;

int main()
{
  int n, k, s = 0, d;
  cout << "Enter a number:";
  cin >> n;
  s = 0;
  k = n;
  while (k > 9)
  {
    while (k != 0)
    {
      d = k % 10;
      s += d;
      k /= 10;
    }
    k = s;
    s = 0;
  }
  if (k == 1)
    cout << n << " is a happy number" << endl;
  else
    cout << n << " is not a happy number" << endl;
  return 0;
}