finish binary tree tilt

12-50/binary-tree-tilt/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "binary-tree-tilt"
+version = "0.1.0"
+authors = ["Checky Hu <[email protected]>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

12-50/binary-tree-tilt/src/main.rs

@@ -0,0 +1,54 @@
+use std::cell::RefCell;
+use std::rc::Rc;
+
+#[derive(Debug, PartialEq, Eq)]
+struct TreeNode {
+    val: i32,
+    left: Option<Rc<RefCell<TreeNode>>>,
+    right: Option<Rc<RefCell<TreeNode>>>,
+}
+
+impl TreeNode {
+    #[inline]
+    fn new(val: i32) -> Self {
+        TreeNode {
+            val,
+            left: None,
+            right: None,
+        }
+    }
+}
+
+struct Solution {}
+
+impl Solution {
+    fn find_tilt_loop(node: Option<&Rc<RefCell<TreeNode>>>) -> (i32, i32) {
+        if let Some(x) = node {
+            let val = x.borrow();
+            let left = Solution::find_tilt_loop(val.left.as_ref());
+            let right = Solution::find_tilt_loop(val.right.as_ref());
+            (
+                left.0 + right.0 + val.val,
+                left.1 + right.1 + (left.0 - right.0).abs(),
+            )
+        } else {
+            (0, 0)
+        }
+    }
+
+    pub fn find_tilt(root: Option<Rc<RefCell<TreeNode>>>) -> i32 {
+        // (sum, tilt)
+        let result = Solution::find_tilt_loop(root.as_ref());
+        result.1
+    }
+}
+
+fn main() {
+    let mut node = TreeNode::new(1);
+    node.left = Some(Rc::new(RefCell::new(TreeNode::new(2))));
+    node.right = Some(Rc::new(RefCell::new(TreeNode::new(3))));
+    println!(
+        "Tilt: {}",
+        Solution::find_tilt(Some(Rc::new(RefCell::new(node))))
+    );
+}