Merge pull request #2564 from xingyiteng/leetcode101

Update 0101.对称二叉树.md 交换顺序

Author: youngyangyang04

problems/0101.对称二叉树.md

@@ -224,8 +224,8 @@ public:
         st.push(root->left);
         st.push(root->right);
         while (!st.empty()) {
-            TreeNode* leftNode = st.top(); st.pop();
             TreeNode* rightNode = st.top(); st.pop();
+            TreeNode* leftNode = st.top(); st.pop();
             if (!leftNode && !rightNode) {
                 continue;
             }
@@ -950,3 +950,4 @@ public bool IsSymmetric(TreeNode root)
 <a href="https://programmercarl.com/other/kstar.html" target="_blank">
   <img src="../pics/网站星球宣传海报.jpg" width="1000"/>
 </a>
+