Inversion of a point around another point

point_inversion.cc

//point inversion
#include <vector>
#include <iostream>

struct Point { int x, y; };
struct Line { Point petal, center; };

//reflects Point 'mover' across another Point 'focus'.
//'focus' is the midpoint of 'mover' and the return value.
Point invert_point(const Point mover, const Point focus){
  return Point{2 * focus.x - mover.x, 2 * focus.y - mover.y};
}

int main() 
{
  std::vector<Line> lines;
  std::vector<Point> mirror;
  int count;
  std::cin >> count;
  lines.reserve(count);
  mirror.reserve(count);
  Line tmpL;
  Point tmpP;
  while(std::cin >> tmpL.petal.x >> tmpL.petal.y >> tmpL.center.x >> tmpL.center.y)
    lines.push_back(tmpL);

  for(auto& l : lines)
    mirror.push_back(invert_point(l.petal, l.center));
  
  for(const auto& p : mirror)
    std::cout << p.x << ' ' << p.y << '\n';
}