Update 0513.找树左下角的值.md

problems/0513.找树左下角的值.md

@@ -621,6 +621,43 @@ impl Solution {
 }
 ```
 
+**递归**
+
+```rust
+use std::cell::RefCell;
+use std::rc::Rc;
+impl Solution {
+    //*递归*/
+    pub fn find_bottom_left_value(root: Option<Rc<RefCell<TreeNode>>>) -> i32 {
+        let mut res = 0;
+        let mut max_depth = i32::MIN;
+        Self::traversal(root, 0, &mut max_depth, &mut res);
+        res
+    }
+    fn traversal(
+        root: Option<Rc<RefCell<TreeNode>>>,
+        depth: i32,
+        max_depth: &mut i32,
+        res: &mut i32,
+    ) {
+        let node = root.unwrap();
+        if node.borrow().left.is_none() && node.borrow().right.is_none() {
+            if depth > *max_depth {
+                *max_depth = depth;
+                *res = node.borrow().val;
+            }
+            return;
+        }
+        if node.borrow().left.is_some() {
+            Self::traversal(node.borrow().left.clone(), depth + 1, max_depth, res);
+        }
+        if node.borrow().right.is_some() {
+            Self::traversal(node.borrow().right.clone(), depth + 1, max_depth, res);
+        }
+    }
+}
+```
+
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