[feat ]: leetcode 129

Signed-off-by: Bo-Wei Chen(BWbwchen) <tim.chenbw@gmail.com>

Author: BWbwchen

leetcode/0129_Sum-Root-to-Leaf-Numbers.rs

@@ -0,0 +1,43 @@
+// Definition for a binary tree node.
+// #[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
+//     }
+//   }
+// }
+use std::rc::Rc;
+use std::cell::RefCell;
+impl Solution {
+    pub fn sum_numbers(root: Option<Rc<RefCell<TreeNode>>>) -> i32 {
+        Self::solve(root, 0)
+    }
+    fn solve(root: Option<Rc<RefCell<TreeNode>>>, base: i32) -> i32 {
+        let mut ret = 0;
+
+        if let Some(root) = root {
+            // check whether it is leaf node
+            let mut node = root.borrow_mut();
+
+            if node.left.is_none() && node.right.is_none() {
+                ret = 10 * base + node.val;
+            } else {
+                let left = Self::solve(node.left.take(), 10 * base + node.val);
+                let right = Self::solve(node.right.take(), 10 * base + node.val);
+                ret = left + right;
+            }
+        }
+
+        ret
+    }
+}