Given the root
of a binary tree, return the sum of every tree node's tilt.
The tilt of a tree node is the absolute difference between the sum of all left subtree node values and all right subtree node values. If a node does not have a left child, then the sum of the left subtree node values is treated as 0
. The rule is similar if there the node does not have a right child.
Example 1:
Input: root = [1,2,3] Output: 1 Explanation: Tilt of node 2 : |0-0| = 0 (no children) Tilt of node 3 : |0-0| = 0 (no children) Tile of node 1 : |2-3| = 1 (left subtree is just left child, so sum is 2; right subtree is just right child, so sum is 3) Sum of every tilt : 0 + 0 + 1 = 1
Example 2:
Input: root = [4,2,9,3,5,null,7] Output: 15 Explanation: Tilt of node 3 : |0-0| = 0 (no children) Tilt of node 5 : |0-0| = 0 (no children) Tilt of node 7 : |0-0| = 0 (no children) Tilt of node 2 : |3-5| = 2 (left subtree is just left child, so sum is 3; right subtree is just right child, so sum is 5) Tilt of node 9 : |0-7| = 7 (no left child, so sum is 0; right subtree is just right child, so sum is 7) Tilt of node 4 : |(3+5+2)-(9+7)| = |10-16| = 6 (left subtree values are 3, 5, and 2, which sums to 10; right subtree values are 9 and 7, which sums to 16) Sum of every tilt : 0 + 0 + 0 + 2 + 7 + 6 = 15
Example 3:
Input: root = [21,7,14,1,1,2,2,3,3] Output: 9
Constraints:
[0, 104]
.-1000 <= Node.val <= 1000
struct Solution;
use rustgym_util::*;
trait Tilt {
fn find_tilt(&self, tilt: &mut i32) -> i32;
}
impl Tilt for TreeLink {
fn find_tilt(&self, tilt: &mut i32) -> i32 {
if let Some(node) = self {
let node = node.borrow();
let left = &node.left;
let right = &node.right;
let left_sum = left.find_tilt(tilt);
let right_sum = right.find_tilt(tilt);
*tilt += (left_sum - right_sum).abs();
node.val + left_sum + right_sum
} else {
0
}
}
}
impl Solution {
fn find_tilt(root: TreeLink) -> i32 {
let mut tilt = 0;
root.find_tilt(&mut tilt);
tilt
}
}
#[test]
fn test() {
let root = tree!(1, tree!(2), tree!(3));
assert_eq!(Solution::find_tilt(root), 1);
}