use crate::share::TreeNode;
use std::cell::RefCell;
use std::rc::Rc;
 impl Solution {
    pub fn postorder_traversal(root: Option<Rc<RefCell<TreeNode>>>) -> Vec<i32> {
        let mut v = Vec::new();
        Solution::traversal(root, &mut v);
        return v;
    }
    fn traversal(root: Option<Rc<RefCell<TreeNode>>>, v: &mut Vec<i32>) {
        if let Some(r) = root {
            Solution::traversal(r.borrow().left.clone(), v);
            Solution::traversal(r.borrow().right.clone(), v);
            v.push(r.borrow().val);
        }
    }
}
#[cfg(test)]
mod test {
    use super::*;
    use crate::share::build_tree;
    use crate::share::NULL;
    #[test]
    fn test_inorder_traversal() {
        let t = build_tree(&vec![1, NULL, 2, NULL, NULL, 3]);
        println!("t={:?}", t);
        assert_eq!(Solution::postorder_traversal(t), vec![3, 2, 1]);
    }
}