Update README.md

lewis liu · web-flow · commit 5fe1c8ed01d2 · 2017-03-10T19:02:38.000+08:00
diff --git a/README.md b/README.md
@@ -34,7 +34,7 @@
 
 [JavaScript 版数据结构与算法（九）排序和搜索](https://lewis617.github.io/2017/02/20/sort-and-search/)
 
-## 练习
+## 拓展
 
 [数组搜索算法题：求和为定值的多个数](https://lewis617.github.io/2017/03/09/n-sum/)
 
