pq.cxx

#include <queue>
#include <vector>
#include <cmath>
#include <iostream>

struct p{ double x,y; char data; };

auto main() -> int
{
  std::vector<p> ps
  { { 0, 0, 'a' }
  , { 0, 1, 'b' }
  , { 1, 1, 'c' }
  , { -0.5, -0.5, 'd' }
  , { 0, 0.75, 'e' }
  };
  
  const p n{ 0.5, 0.5, 'N' };
  
  const auto comparer = [n](const p* pa, const p* pb )
  {
    const auto distance = [n](const p* px)
    {
      const auto dx = px->x - n.x;
      const auto dy = px->y - n.y;
      return std::sqrt( dx * dx + dy * dy );
    };
    return distance(pa) > distance(pb);
  };
  
  std::priority_queue<const p*, std::vector<const p*>, decltype(comparer)> pp(comparer);
  
  for ( const auto& p : ps )
  {
    pp.emplace( &p );
    std::cout << p.data;
  }
  std::cout << "\n";

  while( not pp.empty() )
  {
    const auto rp = pp.top();
    std::cout << rp->data;
    pp.pop();
  }
  std::cout << "\n";
}