Update README.md

rogertan30 · web-flow · commit 1b7e69b2bd0f · 2019-12-19T19:56:41.000+08:00
diff --git a/README.md b/README.md
@@ -11,3 +11,5 @@
 [小码哥《恋上数据结构与算法》笔记（五）：栈](https://juejin.im/post/5dfb12fd518825122e0a85bd)
 
 [小码哥《恋上数据结构与算法》笔记（六）：队列](https://juejin.im/post/5dfb1fc4e51d4557f26e601b)
+
+[小码哥《恋上数据结构与算法》笔记（七）：二叉树](https://juejin.im/post/5dfb4f07f265da33985632f9)
