Function insert

code/data-structures/cartesian_tree.cpp:29–33

    else return t; }
  return NULL; }
node* insert(node *t, int x, int y) {
  if (find(t, x) != NULL) return t;
  pair<node*,node*> res = split(t, x);
  return merge(res.first,
      merge(new node(x, y), res.second)); }
node* erase(node *t, int x) {
  if (!t) return NULL;
  if (t->x < x) t->r = erase(t->r, x);