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diff --git a/Diff for: ‎SUMMARY.md
+5-1 b/Diff for: ‎SUMMARY.md
+5-1
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 ‌
 # Summary
 
+## 前言
+
+* [使用指南](introduction.md)
+
 ## 高频考题（简单）
 * [面试题 17.12. BiNode](./problems/binode-lcci.md)
 * [0001.two-sum](https://github.com/azl397985856/leetcode/blob/mast./problems/1.two-sum.md)
@@ -211,7 +215,7 @@
 * [双指针](https://lucifer.ren/blog/2020/05/26/91algo-basic-05.two-pointer/)
 * [第二期](https://lucifer.ren/blog/2000/04/06/91-algo-2/)
 
-## 精选题解
+##  精选题解
 
 * [《日程安排》专题](https://lucifer.ren/blog/2020/02/03/leetcode-%E6%88%91%E7%9A%84%E6%97%A5%E7%A8%8B%E5%AE%89%E6%8E%92%E8%A1%A8%E7%B3%BB%E5%88%97/)
 * [《构造二叉树》专题](https://lucifer.ren/blog/2020/02/08/%E6%9E%84%E9%80%A0%E4%BA%8C%E5%8F%89%E6%A0%91%E4%B8%93%E9%A2%98/)