Update 二叉树理论基础.md

problems/二叉树理论基础.md

@@ -275,15 +275,15 @@ rust:
 
 ```rust
 #[derive(Debug, PartialEq, Eq)]
-pub struct TreeNode {
-    pub val: i32,
-    pub left: Option<Rc<RefCell<TreeNode>>>,
-    pub right: Option<Rc<RefCell<TreeNode>>>,
+pub struct TreeNode<T> {
+    pub val: T,
+    pub left: Option<Rc<RefCell<TreeNode<T>>>>,
+    pub right: Option<Rc<RefCell<TreeNode<T>>>>,
 }
 
-impl TreeNode {
+impl<T> TreeNode<T> {
     #[inline]
-    pub fn new(val: i32) -> Self {
+    pub fn new(val: T) -> Self {
         TreeNode {
             val,
             left: None,