030.cpp

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

const int MAX = 7;
class digits
{
  unsigned short x[MAX];
public:
    digits ();
  void next ();
  bool end ();
  unsigned f ();
  bool operator== (unsigned fx);
};
digits::digits ()
{
  x[0] = x[1] = 1;
  for (int i = 2; i < MAX; i++)
    x[i] = 0;
}


unsigned
digits::f ()
{
  unsigned sum_of_powers = 0;
  for (int i = 0; i < MAX; i++)
    {
      unsigned short d = x[i];
      sum_of_powers += d * d * d * d * d;
    }
  return sum_of_powers;
}

void
digits::next ()
{
  int i = 0;
  while (x[i] == 9 && i < MAX)
    i++;
  if (i == MAX)                 //overflow
    {
      x[MAX - 1] = 10;
      return;
    }
  else
    {
      x[i]++;
      while (i > 0)
        {
          x[i - 1] = x[i];
          i--;
        }
    }
}

bool
digits::end ()
{
  return (x[MAX - 1] == 10);
}

bool
digits::operator== (unsigned fx)
{
  unsigned short y[MAX];
  copy (x, x + MAX, y);
  for (; fx > 0; fx /= 10)
    {
      unsigned short d = fx % 10;
      if (d == 0)
        continue;
      unsigned short *p = find (y, y + MAX, d);
      if (p == y + MAX)
        return 0;               //return false
      else
        *p = 0;
    }

  for (int i = 0; i < MAX; i++)
    if (y[i] != 0)
      return 0;                 //check if list is empty

  return 1;
}

int
main ()
{
  unsigned sum = 0;
  for (digits X; !X.end (); X.next ())
    {
      unsigned fx = X.f ();
      if (X == fx)
        sum += fx;
    }
  cout << sum << endl;
  return 0;
}