Given the root of a binary tree, return the number of uni-value subtrees.
A uni-value subtree means all nodes of the subtree have the same value.
Example 1:
Input: root = [5,1,5,5,5,null,5] Output: 4
Example 2:
Input: root = [] Output: 0
Example 3:
Input: root = [5,5,5,5,5,null,5] Output: 6
Constraints:
- The numbrt of the node in the tree will be in the range
[0, 1000]. -1000 <= Node.val <= 1000
struct Solution;
use rustgym_util::*;
trait Postorder {
fn postorder(&self, count: &mut i32) -> Option<i32>;
}
impl Postorder for TreeLink {
fn postorder(&self, count: &mut i32) -> Option<i32> {
if let Some(node) = self {
let node = node.borrow();
let val = node.val;
let left = &node.left;
let right = &node.right;
match (left, right) {
(Some(_), Some(_)) => {
if let (Some(left_val), Some(right_val)) =
(left.postorder(count), right.postorder(count))
{
if left_val == val && right_val == val {
*count += 1;
Some(val)
} else {
None
}
} else {
None
}
}
(Some(_), None) => {
if let Some(left_val) = left.postorder(count) {
if left_val == val {
*count += 1;
Some(val)
} else {
None
}
} else {
None
}
}
(None, Some(_)) => {
if let Some(right_val) = right.postorder(count) {
if right_val == val {
*count += 1;
Some(val)
} else {
None
}
} else {
None
}
}
(None, None) => {
*count += 1;
Some(val)
}
}
} else {
None
}
}
}
impl Solution {
fn count_unival_subtrees(root: TreeLink) -> i32 {
let mut res = 0;
root.postorder(&mut res);
res
}
}
#[test]
fn test() {
let root = tree!(5, tree!(1, tree!(5), tree!(5)), tree!(5, None, tree!(5)));
let res = 4;
assert_eq!(Solution::count_unival_subtrees(root), res);
}