A binary tree is univalued if every node in the tree has the same value.
Return true
if and only if the given tree is univalued.
Example 1:
Input: [1,1,1,1,1,null,1] Output: true
Example 2:
Input: [2,2,2,5,2] Output: false
Note:
[1, 100]
.[0, 99]
.struct Solution;
use rustgym_util::*;
trait Preorder {
fn is_unival(&self) -> bool;
fn preorder(&self, val: &mut Option<i32>) -> bool;
}
impl Preorder for TreeLink {
fn is_unival(&self) -> bool {
let mut val: Option<i32> = None;
self.preorder(&mut val)
}
fn preorder(&self, val: &mut Option<i32>) -> bool {
if let Some(node) = self {
let node = node.borrow();
let node_val = node.val;
if let Some(val) = val {
if *val != node_val {
return false;
}
} else {
*val = Some(node_val);
}
node.left.preorder(val) && node.right.preorder(val)
} else {
true
}
}
}
impl Solution {
fn is_unival_tree(root: TreeLink) -> bool {
root.is_unival()
}
}
#[test]
fn test() {
let root = tree!(1, tree!(1, tree!(1), tree!(1)), tree!(1, None, tree!(1)));
assert_eq!(Solution::is_unival_tree(root), true);
let root = tree!(2, tree!(2, tree!(5), tree!(2)), tree!(2));
assert_eq!(Solution::is_unival_tree(root), false);
}