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use std::rc::Rc;
use std::cell::RefCell;
#[derive(Debug, PartialEq, Eq)]
pub struct TreeNode {
pub val: i32,
pub left: Option<Rc<RefCell<TreeNode>>>,
pub right: Option<Rc<RefCell<TreeNode>>>,
}
impl TreeNode {
#[inline]
pub fn new(val: i32) -> Self {
TreeNode {
val, left: None,
right: None
}
}
}
struct Solution;
impl Solution {
pub fn preorder_traversal(root: Option<Rc<RefCell<TreeNode>>>) -> Vec<i32> {
let mut ans: Vec<i32> = Vec::new();
let mut stack: Vec<Option<Rc<RefCell<TreeNode>>>> = vec![root];
while let Some(last) = stack.pop() {
if let Some(n) = last {
ans.push(n.borrow().val);
stack.push(n.borrow().right.clone());
stack.push(n.borrow().left.clone());
}
}
ans
}
}
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