Номера 1 и 2 к 21.05, Кузичкин 141 группа

#include <algorithm>
#include <vector>
#include <cmath>
#include <iostream>

using namespace std;

class Point
{
private:
  int x, y, z;
public:
  friend bool operator<(const Point& p)
  {
    return (sqrt(x * x + y * y + z * z) < sqrt(p.x * p.x + p.y * p.y + p.z * p.z));
  }
  friend bool operator>(const Point& p)
  {
    return (sqrt(x * x + y * y + z * z) > sqrt(p.x * p.x + p.y * p.y + p.z * p.z));
  }

  static bool difference(const Point& p)
  {
    return (sqrt(x * x + y * y + z * z) < sqrt(p.x * p.x + p.y * p.y + p.z * p.z));
  }
};

int main()
{
  int n;
  cin >> n;
  vector<Point> pts;
  for (int i = 0; i < n; ++i)
  {
    Point obj;
    int x, y, z;
    cin >> x >> y >> z;
    obj.x = x;
    obj.y = y;
    obj.z = z;
    pts.push_back(obj);
  }
  sort(pts.begin(), pts.end()/*, Point::difference*/)
  //stable_sort(pts.begin(), pts.end()/*, Point::difference*/)
  return 0;
}