diff --git a/baidu/backend.md b/baidu/backend.md
index c219d30..e81f29d 100644
--- a/baidu/backend.md
+++ b/baidu/backend.md
@@ -1,7 +1,8 @@
 | 公司 | 岗位 | 题目                           | 链接                                                                                                  | 频度 |
 |----|----|------------------------------|-----------------------------------------------------------------------------------------------------|----|
-| 百度 | 后端 | 102. 二叉树的层序遍历                | https://leetcode-cn.com/problems/binary-tree-level-order-traversal/                                 | 4  |
+| 百度 | 后端 | 102. 二叉树的层序遍历                | https://leetcode-cn.com/problems/binary-tree-level-order-traversal/                                 | 5  |
 | 百度 | 后端 | 206. 反转链表                    | https://leetcode-cn.com/problems/reverse-linked-list/                                               | 4  |
+| 百度 | 后端 | 剑指 Offer 39. 数组中出现次数超过一半的数字  | https://leetcode-cn.com/problems/shu-zu-zhong-chu-xian-ci-shu-chao-guo-yi-ban-de-shu-zi-lcof/       | 3  |
 | 百度 | 后端 | 94. 二叉树的中序遍历                 | https://leetcode-cn.com/problems/binary-tree-inorder-traversal/                                     | 3  |
 | 百度 | 后端 | 199. 二叉树的右视图                 | https://leetcode-cn.com/problems/binary-tree-right-side-view/                                       | 3  |
 | 百度 | 后端 | 4. 寻找两个正序数组的中位数              | https://leetcode-cn.com/problems/median-of-two-sorted-arrays/                                       | 3  |
@@ -15,7 +16,6 @@
 | 百度 | 后端 | 面试题 01.06. 字符串压缩             | https://leetcode-cn.com/problems/compress-string-lcci/                                              | 2  |
 | 百度 | 后端 | 104. 二叉树的最大深度                | https://leetcode-cn.com/problems/maximum-depth-of-binary-tree/                                      | 2  |
 | 百度 | 后端 | 20. 有效的括号                    | https://leetcode-cn.com/problems/valid-parentheses/                                                 | 2  |
-| 百度 | 后端 | 剑指 Offer 39. 数组中出现次数超过一半的数字  | https://leetcode-cn.com/problems/shu-zu-zhong-chu-xian-ci-shu-chao-guo-yi-ban-de-shu-zi-lcof/       | 2  |
 | 百度 | 后端 | 69. x 的平方根                   | https://leetcode-cn.com/problems/sqrtx/                                                             | 2  |
 | 百度 | 后端 | 449. 序列化和反序列化二叉搜索树           | https://leetcode-cn.com/problems/serialize-and-deserialize-bst/                                     | 1  |
 | 百度 | 后端 | 105. 从前序与中序遍历序列构造二叉树         | https://leetcode-cn.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/         | 1  |