Евгений Шатунов

#include<iostream>
#include<filesystem>
#include<string>

using namespace std;
namespace fs = filesystem;

auto listFilesRecursively = [](auto const& dir, string const& mask = {}){
  if(!fs::is_directory(dir))
  {
    cerr << dir << " is not dir";
    throw "is not dir!";
  }
  
  for(auto const& file : fs::recursive_directory_iterator(dir))
  {
    if(fs::is_regular_file(file))
    {
      if(mask.empty() || file.path().extension().string() == mask)
      {
        // Здесь твоя функция вывода инфы
        cout << file.path().string() << " #size: " << file.file_size() << "\n";
      }
    }
    else if(fs::is_directory(file))
    {
      cout << "\n****** dir ****** [" << file.path().string() << "]\n";
    }
    else
    {
      cout << "\n***** other... ******[" << file.path().filename().string() << "]\n";
    }
  }
};

int main()
{
  const string start_dir = R"(C:\Program Files)";
  try
  {
    listFilesRecursively(start_dir, ".dll");
  }
  catch(exception& e)
  {
    cerr << e.what();
  }
}

#include <algorithm>
#include <iterator>
#include <iostream>
#include <vector>

using namespace std;

auto fx = [](int x){
  int r = 0;
  switch(x % 3)
  {
    case 0:
      r = x * x;
      break;
    case 1:
      r = x;
      break;
    default:
      r = x / 3;
      break;
  }
  return r;
};

auto calculate = [](const vector<int>& vx, auto fx){
  vector<int> calcValues(vx.size());
  transform(vx.begin(), vx.end(), calcValues.begin(), fx);
  return calcValues;
};

int main()
{
  cout << "Введи кол-во чисел: ";
  int n = 0;
  cin >> n;

  cout << "Введи через пробел " << n << " натуральных чисел:\n" << "$: ";
  vector<int> values(n);
  copy_n(istream_iterator<int>(cin), n, values.begin());

  cout << "Результат твоих расчетов:\n";
  copy_n(calculate(values, fx).begin(), n, ostream_iterator<int>(cout, "\n"));
}

#include<iostream>
#include<filesystem>
#include<string>
using namespace std;
namespace fs = filesystem;

auto getDirectorySize(const fs::path& p)
{
  uintmax_t size = 0;
  if(fs::is_directory(p))
  {
    for(const auto& f : fs::directory_iterator(p))
    {
      size += f.file_size();
    }
  }
  return size;
}

int main()
{
  string directory{ "C:\\TEMP" };
  fs::path dp{ directory };
  
  auto size{ getDirectorySize(dp) };
  cout << "size of "  << directory 
       << " "         << size 
       << " bytes"    << endl;
}

#include<iostream>
#include<fstream>
#include<string>
#include<vector>
using namespace std;

size_t getFileSize(const string& filename)
{
  ifstream ifs(filename);
  size_t size = 0;
  if(ifs)
  {
    ifs.seekg(0, ios_base::end);
    size = ifs.tellg();
  }
  return size;
}

int main()
{
  vector<string> filenames{
    "C:\\TEMP\\aaa.txt", "C:\\TEMP\\bbb.txt", "C:\\TEMP\\ccc.txt"
  };

  size_t size = 0;

  for(const string& fn : filenames)
  {
    size += getFileSize(fn);
  }

  cout << "Size: " << size << endl;
}

template<class ForwardIt, class Compare>
ForwardIt min_element(ForwardIt first, ForwardIt last, Compare comp)
{
    if (first == last) return last;
 
    ForwardIt smallest = first;
    ++first;
    for (; first != last; ++first) { // не возвращает значения сразу
        if (comp(*first, *smallest)) { //  каким образом происходит сравнение
            smallest = first;
        }
    }
    return smallest; // а только в конце
}