storing more than 2 power 31 on a 32-bit system

Question

I have to write a program that can calculate the powers of 2 power 2010 and to find the sum of the digits. eg:

if `2 power 12 => gives 4096          


        

Answer 1

Here's how you can calculate and print 2²⁰¹⁰:

#include 
#include 

void AddNumbers(char* dst, const char* src)
{
  char ddigit;
  char carry = 0;

  while ((ddigit = *dst) != '\0')
  {
    char sdigit = '0';

    if (*src != '\0')
    {
      sdigit = *src++;
    }

    ddigit += sdigit - '0' + carry;

    if (ddigit > '9')
    {
      ddigit -= 10;
      carry = 1;
    }
    else
    {
      carry = 0;
    }

    *dst++ = ddigit;
  }
}

void ReverseString(char* s)
{
  size_t i, n = strlen(s);

  for (i = 0; i < n / 2; i++)
  {
    char t = s[i];
    s[i] = s[n - 1 - i];
    s[n - 1 - i] = t;
  }
}

int main(void)
{
  char result[607], tmp[sizeof(result)];
  int i;

  memset (result, '0', sizeof(result));
  result[0] = '1';
  result[sizeof(result) - 1] = '\0';

  for (i = 0; i < 2010; i++)
  {
    memcpy(tmp, result, sizeof(result));
    AddNumbers(result, tmp);
  }

  ReverseString(result);
  printf("%s\n", result);

  return 0;
}

You can now sum up the individual digits.