Function erase

code/data-structures/cartesian_tree.cpp:34–39

  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);
  else if (x < t->x) t->l = erase(t->l, x);
  else { node *old = t; t = merge(t->l, t->r); delete old; }
  if (t) augment(t); return t; }
int kth(node *t, int k) {
  if (k < tsize(t->l)) return kth(t->l, k);
  else if (k == tsize(t->l)) return t->x;