From 5a73c717d0feff558a10b2d5f5ab9834f8fbd64e Mon Sep 17 00:00:00 2001
From: Shine wOng <1551885@tongji.edu.cn>
Date: Tue, 10 Dec 2019 17:52:16 +0800
Subject: [PATCH] again modify some mistakes.

---
 thu_dsa/chp4/notice.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/thu_dsa/chp4/notice.md b/thu_dsa/chp4/notice.md
index 32424c3..7c22a6d 100644
--- a/thu_dsa/chp4/notice.md
+++ b/thu_dsa/chp4/notice.md
@@ -80,7 +80,7 @@ $$
 
 答案当然是错误的，因为这里会产生重复计数的问题。比如设$S_3 = ()()()$，$S_1 = ()$，$S_2 = ()()$，那么$S_3 = S_1S_2 = S_2S_1$，会被计数两次。另一种划分$S_n = S_k()S_{n - k - 1}$也是同样的问题。
 
-因此，这里正确的划分应该是$S_n = (S_k)S_{n - k}$，容易证明，此时没有上面的重复计数情况。此时就可以得到
+因此，这里正确的划分应该是$S_n = (S_k)S_{n - k - 1}$，容易证明，此时没有上面的重复计数情况。此时就可以得到
 
 $$
 SP(n) = \Sigma_{k = 0}^{n - 1}SP(k)SP(n - k - 1)