Big number

/**Define a structure / class to hold a very big number
(way bigger than bigint) and add a member functions to 
increment the number by 1 and decrement the number by 1

- Dee on November 06, 2012 in United States | Report Duplicate */

/**Use an array to simulate bits.
Need to take care of carry's when add/substract.
One trivial bug: negative zero. 
 */
#include <array>
#include <algorithm>
#include <iostream>
using namespace std;

class HugeNumber{
private:
  static const int DIGITS = 1000;
  array<unsigned short, DIGITS> number;//number[0] is the lowest digit
  bool negative_flag;
public:
  HugeNumber(){
    number.fill(0);negative_flag = false;
  }
  
  HugeNumber(int number_int){
    this->assign(number_int);
  }

  HugeNumber(HugeNumber const& n2){
    negative_flag = n2.negative_flag;
    for(unsigned int ii = 0; ii < DIGITS; ++ii)
      number[ii] = n2.number[ii];
  }
  HugeNumber& assign(int number_int){
    negative_flag = (number_int < 0);
    if (negative_flag) number_int = -number_int;
    for(unsigned int ii = 0; number_int; ++ii){
      number[ii] = number_int%10;
      number_int /= 10;
    }
    return *this;
  }//assign
  
  HugeNumber& operator++(){
    if (negative_flag){
      if (count(number.begin(),number.end(), 0) == DIGITS){//0
        negative_flag = false;
        ++number[0];
        return *this;
      }
      negative_flag = false;
      --(*this); 
      negative_flag = true;
      return (*this);
    }
    ++number[0];
    for(unsigned int ii = 0; ii < DIGITS-1 && number[ii] >= 10; ++ii){
      number[ii] -= 10;
      ++number[ii+1];
    }
    return *this;
  }

  HugeNumber& operator--(){
    if (count(number.begin(), number.end(), 0) == DIGITS){
      negative_flag = true;
      ++number[0];
      return *this;
    }
    if (negative_flag){
      negative_flag = false;
      ++(*this);
      negative_flag = true;
      return (*this);
    }
    for(unsigned int ii = 0; ii < DIGITS; ++ii){
      number[ii] = 9 - number[ii];
    }
    ++(*this);
    for(unsigned int ii = 0; ii < DIGITS; ++ii){
      number[ii] = 9 - number[ii];
    }
    return *this;
  }

  void output(ostream& os) const{
    if (negative_flag) os<<'-';
    for(unsigned int ii = DIGITS-1; ii > 0; --ii){
      if (!number[ii]) continue;
      os<<number[ii];
    }
    os<<number[0];//in case all digits are zero
  }

};

ostream& operator<<(ostream& os, HugeNumber& const number){
  number.output(os);
  return os;
}

int main(){
  cout<<"hello"<<endl;
  HugeNumber hn;
  hn.assign(-2);
  cout<<hn<<endl;
  ++hn;
  cout<<hn<<endl;
  ++hn;
  cout<<hn<<endl;
  ++hn;
  cout<<hn<<endl;
  ++hn;
  cout<<hn<<endl;
  ++hn;
  cout<<hn<<endl;
  --hn;
  cout<<hn<<endl;
  --hn;
  cout<<hn<<endl;
  --hn;
  cout<<hn<<endl;
  --hn;
  cout<<hn<<endl;
  --hn;
  cout<<hn<<endl;
  return 0;
}