Распарсить строку, найти числа. произвести арифметические операции

int main()
    {
    string a = "21,22,23,24";
    string buff;
    int aa = 55;
    for (int x = 0; x <=a.size(); x++)
    {
        if (a[x] == ',' || a[x]=='\0')
        {
            cout << aa + atoi(buff.c_str())<<endl;
            buff = "";
        }
        else
            buff += a[x];
    }
    system("Pause");
        return 0;
    }

#include <boost/algorithm/string.hpp>
#include <boost/lexical_cast.hpp>
#include <vector>
#include <string>
#include <algorithm>
#include <iterator>
#include <iostream>
 
int main()
{
   const std::string a = "21,22,23,24";
   std::vector<std::string> words;
   boost::split(words, a, boost::is_any_of(","), boost::token_compress_on);
   std::vector<int> numbers;
   std::transform(words.begin(), words.end(), std::back_inserter(numbers), &boost::lexical_cast<int, std::string>);
   std::copy(numbers.begin(), numbers.end(), std::ostream_iterator<int>(std::cout, "\n"));
}

TStringList *LinkedAnalog = new TStringList();
LinkedAnalog->Clear();
LinkedAnalog->Delimiter = ',';
for (int i = 0; i < Result->RowCount-1; i++)
{
  if(Result->Cells[4][i+1]!="")
  {
    LinkedAnalog->DelimitedText = Result->Cells[4][i+1];
    for(int k = 0; k < LinkedAnalog->Count; k++)
    {
     Result->Cells[4][i+1]=IntToStr(LinkedAnalog->Strings[k].ToInt()- OffsetAnalog->Value);
    }
  }
}
delete LinkedAnalog;
LinkedAnalog = NULL;

int main()
    {
    string a = "21,22,23,24";
    for (int x = 0; x <= a.size(); x++)
        cout <<std::hex<<(int) a[x]<<" ";
    system("Pause");
        return 0;
    }

reference       operator[]( size_type pos );
const_reference operator[]( size_type pos ) const;