[feat ]: leetcode 404

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

Author: BWbwchen

leetcode/0404_Sum-of-Left-Leaves.rs

@@ -0,0 +1,51 @@
+// 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;
+#[derive(Copy, Clone)]
+enum DIR {
+    LEFT,
+    RIGHT,
+}
+impl Solution {
+    pub fn sum_of_left_leaves(root: Option<Rc<RefCell<TreeNode>>>) -> i32 {
+        Self::solve(root, DIR::RIGHT)
+    }
+    fn solve(root: Option<Rc<RefCell<TreeNode>>>, dir: DIR) -> i32 {
+        let mut ret = 0;
+        if let Some(root) = root {
+            let mut node = root.borrow_mut();
+            if node.left.is_none() && node.right.is_none() {
+                // leaf node
+                ret = match dir {
+                    DIR::LEFT => node.val,
+                    _ => 0,
+                };
+            } else {
+                let left = Self::solve(node.left.take(), DIR::LEFT);
+                let right = Self::solve(node.right.take(), DIR::RIGHT);
+
+
+                ret = left + right;
+            }
+        }
+        ret
+    }
+
+}