struct Node<T: Ord> {
    data : T,

    left : Option<Box<Node<T>>>,
    right : Option<Box<Node<T>>>,
}

impl<T: Ord> Node<T> {
    pub fn new(data : T) -> Self {
        Node{
            data,
            left: None,
            right: None,
        }
    }

}

fn main() {
    // Setup a binary tree
    let mut parent = Box::new(Node::new(15));
    parent.left = Some(Box::new(Node::new(7)));

    if let Some(ref mut left) = parent.left {
        left.left = Some(Box::new(Node::new(3)));
    }

    parent.right = Some(Box::new(Node::new(30)));

    use std::collections::VecDeque;

    // Loop through a binary tree
    let mut stack = Vec::new(); 
    let mut current = Some(&parent);
    while current.is_some() || !stack.is_empty() {
        while current.is_some() {
            stack.push(current);
            current = current.unwrap().left.as_ref();
        }

        current = stack.pop().unwrap();
        dbg!(current.unwrap().data);

        current = current.unwrap().right.as_ref();
    }

    println!("Still can use parent here!");
    dbg!(parent.data);
}