Why b = 10 and not 11?

Question

C++ / C#

int a = 5;
  int b;
  b = 2 * a++;
  std::cout << b << std::endl;
  std::cout << a;

Answer 1

std::vector<std::string> vct;
std::sort(vct.begin(), vct.end());

Answer 2

Generally speaking, C++ doesn't sort strings like that, since they're non-PODs. In fact, in this case, qsort swaps the internals of std::string, which cannot be done directly (UB).
Sorting non-POD types is done with std::sort.
Anyway, std::sort is a template function; it is better to inline than qsort, and therefore it is better to use it in C++ code.

#include <string>
#include <cstdlib>
#include <iostream>
#include <algorithm>

int str_compare(std::string const & l, std::string const & r)
{
  if (l == r)
    return 0;
  return l < r ? -1 : 1;
}
int str_compare(void const * l, void const * r) { return str_compare(*static_cast<std::string const *>(l), *static_cast<std::string const *>(r)); }

int main()
{
  std::string strs[3] = { "foo", "bar", "baz" };
  std::qsort(strs, 3, sizeof(std::string), str_compare); // В общем, работает, но UB
  // std::sort(&strs[0], &strs[0] + 3); // вот так - лучше
  for (auto & s : strs)
    std::cout << s << std::endl;
    return 0;
}

Answer 3

i think instead of const void *a you need const void& a

Answer 4

Because post-increment ++ only applies to a .