6.28

/*6.28
Deitel & Deitel C++ How to Program, 10th ed(Indian subcontinent adaptation)
Visual Studio Community 2019
*/

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

bool isDudeney(unsigned long testNum, unsigned long cubed) {
   unsigned long sum{ 0 };
   int digit{ 0 };
   for (unsigned long divisor = 1'000'000'000; divisor >= 10; divisor /= 10) {
      if (testNum >= divisor) {
         sum += testNum / divisor;
      }
      testNum %= divisor;
   }
   sum += testNum; // at this point testNum should be the digit in the one's position
   if (sum == cubed) return true;
   else return false;
}

int main() {
   unsigned long testnum;
   int dudeneyCtr{ 0 };
   unsigned long cubedroot;

   // check up to 100 million
   for (testnum = 0; testnum < 100'000'000; testnum++) {
      if (testnum > 0 && testnum % 10'000'000 == 0) cout << testnum << endl; // give some feedback

      cubedroot = cbrt(testnum);
      if (cubedroot * cubedroot * cubedroot == testnum) {
         if (isDudeney(testnum, cubedroot)) {
            cout << testnum << " is a Dudeney. Its cube root is " << cubedroot << endl;
            dudeneyCtr++;
         }
      }
   }
   cout << endl << "Count of Dudeney numbers: " << dudeneyCtr << endl;
   return 0;
}