void checkCase4(Node *child, Node *grand) {
 if (child == child->parent->right && child->parent == grand->left) {
  rotate_left(grand, child->parent, child);
  child = child->left;
 }
 else if (child == child->parent->left && child->parent == grand->right) {
  rotate_right(grand, child->parent, child);
  child = child->right;
 }
 checkCase5(child, child->parent->parent);
}

void Tree::rotate_right(Node *gr, Node *par, Node *ch){
...
}