程序代码：

// skipws flag example
#include <iostream>     // std::cout, std::skipws, std::noskipws
#include <sstream>      // std::istringstream

int main () {
  char a, b, c;

  std::istringstream iss (" 12 3");
  iss >> std::skipws >> a >> b >> c;
  std::cout << a << b << c << '\n';

  iss.seekg(0);//这一句删去后得到结果怎么解释？ 
  iss >> std::noskipws >> a >> b >> c;
  std::cout << a << b << c << '\n';
  return 0;
}