fix bug

Author: checkcheckzz

README.md

@@ -156,6 +156,7 @@ By default, the time complexity is the worst time and the space complexity doesn
 * Trim binary search tree
 * [Total weight of a subtree below this node](https://github.com/checkcheckzz/coding-problems/blob/master/problem/Totalweight.cpp)
 * [Vertical sum in a binary tree](https://github.com/checkcheckzz/coding-problem/blob/master/problem/Tree/Vertical%20sum%20in%20a%20binary%20tree.cpp)
+
 --
 ####[[⬆]](#toc) <a name='math'>Math:</a>