Method _con

code/data-structures/kd_tree.cpp:55–59

            construct(pts, mid + 1, to, INC(c))); }
  bool contains(const pt &p) { return _con(p, root, 0); }
  bool _con(const pt &p, node *n, int c) {
    if (!n) return false;
    if (cmp(c)(p, n->p)) return _con(p, n->l, INC(c));
    if (cmp(c)(n->p, p)) return _con(p, n->r, INC(c));
    return true; }
  void insert(const pt &p) { _ins(p, root, 0); }
  void _ins(const pt &p, node* &n, int c) {
    if (!n) n = new node(p, NULL, NULL);