readme updated.

liuyubobobo · liuyubobobo · commit 056e5ea0c6ef · 2017-06-16T11:20:08.000-07:00
diff --git a/README.md b/README.md
@@ -113,6 +113,7 @@
 | 6-6 路径压缩（Path Compression）| [C++源码](https://github.com/liuyubobobo/Play-with-Algorithms/tree/master/06-Union-Find/Course%20Code%20(C%2B%2B)/06-Path-Compression) | [Java源码](https://github.com/liuyubobobo/Play-with-Algorithms/tree/master/06-Union-Find/Course%20Code%20(Java)/06-Path-Compression/src/bobo/algo) |
 | 本章课程最终代码 | [C++源码](https://github.com/liuyubobobo/Play-with-Algorithms/tree/master/06-Union-Find/Course%20Code%20(C%2B%2B)/Chapter-06-Completed-Code) | [Java源码](https://github.com/liuyubobobo/Play-with-Algorithms/tree/master/06-Union-Find/Course%20Code%20(Java)/Chapter-06-Completed-Code/src/bobo/algo) |
 | 补充1 使用相同的测试用例测试不同的UF实现 | [C++源码](https://github.com/liuyubobobo/Play-with-Algorithms/tree/master/06-Union-Find/Course%20Code%20(C%2B%2B)/Optional-01-Same-Cases-Test-for-UF) | [Java源码](https://github.com/liuyubobobo/Play-with-Algorithms/tree/master/06-Union-Find/Course%20Code%20(Java)/Optional-01-Same-Cases-Test-for-UF/src/bobo/algo) |
+| 补充2 迭代和递归实现两种路径压缩的区别 | [C++源码](https://github.com/liuyubobobo/Play-with-Algorithms/tree/master/06-Union-Find/Course%20Code%20(C%2B%2B)/Optional-02-Path-Compression-Comparison) | [Java源码](https://github.com/liuyubobobo/Play-with-Algorithms/tree/master/06-Union-Find/Course%20Code%20(Java)/Optional-02-Path-Compression-Comparison/src/bobo/algo) |
 | **第七章 图的基础** | [章节C++源码](https://github.com/liuyubobobo/Play-with-Algorithms/tree/master/07-Graph-Basics/Course%20Code%20(C%2B%2B)) | [章节Java源码](https://github.com/liuyubobobo/Play-with-Algorithms/tree/master/07-Graph-Basics/Course%20Code%20(Java)) |
 | 7-1 图论基础 | [无代码] |  |
 | 7-2 图的表示 | [C++源码](https://github.com/liuyubobobo/Play-with-Algorithms/tree/master/07-Graph-Basics/Course%20Code%20(C%2B%2B)/02-Graph-Representation) | [Java源码](https://github.com/liuyubobobo/Play-with-Algorithms/tree/master/07-Graph-Basics/Course%20Code%20(Java)/02-Graph-Representation/src/bobo/algo) |
