Code shared from the Rust Playground

playground.rs

use std::rc::{Rc,Weak};
use std::cell::RefCell;

#[derive(Debug)]
struct Node {
    value: i32,
    parent: RefCell<Weak<Node>>,
    children: RefCell<Vec<Rc<Node>>>,
}

fn main() {

    let leaf = Rc::new(Node {
        value: 3,
        children: RefCell::new(vec![]),
        parent: RefCell::new(Weak::new()),
    });
    
    println!(
        "leaf strong = {} weak = {}", 
        Rc::strong_count(&leaf),
        Rc::weak_count(&leaf)
    );
    
    {
        
        
        let branch = Rc::new(Node{
            value:5,
            children: RefCell::new(vec![Rc::clone(&leaf)]),
            parent: RefCell::new(Weak::new()),
        });
        
        *leaf.parent.borrow_mut() = Rc::downgrade(&branch);
        
        println!(
            "branch strong = {} weak = {}",
            Rc::strong_count(&branch),
            Rc::weak_count(&branch),
        );
        
        println!(
            "leaf strong = {} weak = {}", 
            Rc::strong_count(&leaf),
            Rc::weak_count(&leaf)
        );
    
    }
    
    println!("leaf parent = {:#?}", leaf.parent.borrow().upgrade());
    println!(
        "leaf strong = {} weak = {}",
        Rc::strong_count(&leaf),
        Rc::weak_count(&leaf),
    );
}