void preorderHelper (TreeNode* node, vector<int>& v) {
if (!node)
return;
v.push_back(node->val);
preorderHelper(node->left, v);
preorderHelper(node->right, v);
}
void BST::preorderHelper(Node *node){
if(node == NULL){
return;
}
else{
cout<<node->data<<"->";
preorderHelper(node -> left);
preorderHelper(node -> right);
}
}
//Preorder Traversal of BST
void BST::preorder(){
if(root == NULL){
cout<<"BST empty";
}
else{
cout<<endl<<"Preorder Traversal"<<endl;
preorderHelper(root);
}
}
vector<int> preorderTraversal(TreeNode* root) {
vector<int> v;
preorderHelper(root, v);
return v;
}
