diff --git a/problems/0236.二叉树的最近公共祖先.md b/problems/0236.二叉树的最近公共祖先.md
index 7b5deb56..41e12df4 100644
--- a/problems/0236.二叉树的最近公共祖先.md
+++ b/problems/0236.二叉树的最近公共祖先.md
@@ -249,7 +249,6 @@ class Solution {
 ```java
 // 代码精简版
 class Solution {
-    TreeNode pre;
     public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
         if (root == null || root.val == p.val ||root.val == q.val) return root;
         TreeNode left = lowestCommonAncestor(root.left,p,q);
diff --git a/problems/0513.找树左下角的值.md b/problems/0513.找树左下角的值.md
index 27c6e83c..7e48b53c 100644
--- a/problems/0513.找树左下角的值.md
+++ b/problems/0513.找树左下角的值.md
@@ -9,6 +9,8 @@
 
 ## 513.找树左下角的值
 
+题目地址：[https://leetcode-cn.com/problems/find-bottom-left-tree-value/](https://leetcode-cn.com/problems/find-bottom-left-tree-value/v)
+
 给定一个二叉树，在树的最后一行找到最左边的值。
 
 示例 1: