diff --git a/.obsidian/plugins/obsidian-style-settings/data.json b/.obsidian/plugins/obsidian-style-settings/data.json
index afb4657..cb2487c 100644
--- a/.obsidian/plugins/obsidian-style-settings/data.json
+++ b/.obsidian/plugins/obsidian-style-settings/data.json
@@ -1,6 +1,6 @@
 {
-  "obsidian-prism-theme@@color-schemes-lt": "pt-color-scheme-periwinkle-lt",
-  "obsidian-prism-theme@@light-accent-color-preset": "pt-accent-color-purple-lt",
+  "obsidian-prism-theme@@color-schemes-lt": "pt-color-scheme-pistachio-lt",
+  "obsidian-prism-theme@@light-accent-color-preset": "pt-accent-color-green-lt",
   "obsidian-prism-theme@@color-schemes-dt": "pt-color-scheme-indigo-dt",
   "obsidian-prism-theme@@pt-disable-blur": true,
   "obsidian-prism-theme@@pt-disable-animations": true,
diff --git a/OJ notes/OJ-index.md b/OJ notes/OJ-index.md
index 834df19..ac5efad 100644
--- a/OJ notes/OJ-index.md	
+++ b/OJ notes/OJ-index.md	
@@ -33,6 +33,12 @@ This is where I store notes about CS
 #CS_list_need_practicing
 ```
 
+#### Topics that needs care
+
+- #sliding_window 
+- #Kadane_s_algorithm 
+- #greedy 
+
 ## Websites
 
 #### [leetcode.com](https://leetcode.com)
diff --git a/OJ notes/pages/Leetcode Subarray-Sum-Equals-K.md b/OJ notes/pages/Leetcode Subarray-Sum-Equals-K.md
index 1ea15fb..2a74981 100644
--- a/OJ notes/pages/Leetcode Subarray-Sum-Equals-K.md	
+++ b/OJ notes/pages/Leetcode Subarray-Sum-Equals-K.md	
@@ -4,11 +4,11 @@
 
 > ##### Algorithms:
 >
-> #algorithm #sliding_window #hash_table 
+> #algorithm #hash_table 
 >
 > ##### Data structures:
 >
-> #DS
+> #DS #array 
 >
 > ##### Difficulty:
 >
@@ -55,13 +55,16 @@ A subarray is a contiguous **non-empty** sequence of elements within an array.
 ### Thoughts
 
 > [!summary]
-> This can be solved using #sliding_window 
+> This can be solved using #prefix_sum and #hash_table 
 
 > I over-complicated the solution by adding stuff like 
 > sorting, but it turn out to be not so difficult.
 
-Since the subsets are **contiguous**, we can use sliding 
-window here.
+> [!tip]
+> Tried using sliding window, but it doesn't work because of 
+> negative numbers.
+
+
 
 ### Solution
 
@@ -100,4 +103,4 @@ public:
     return count;
   }
 };
-```
\ No newline at end of file
+```
diff --git a/OJ notes/pages/Two pointers approach.md b/OJ notes/pages/Two pointers approach.md
index f70a55f..0a285d9 100644
--- a/OJ notes/pages/Two pointers approach.md	
+++ b/OJ notes/pages/Two pointers approach.md	
@@ -14,13 +14,14 @@
 
 ##### Difficulty:
 
-#CS_analysis #difficulty-
+#CS_analysis
 
 ##### Related problems:
 
 ##### Links:
 
 - [leetcode](https://leetcode.com/explore/learn/card/fun-with-arrays/511/in-place-operations/)
+- [Two-pointers and sliding windows](https://leetcode.com/problems/subarray-sum-equals-k/discuss/301242/General-summary-of-what-kind-of-problem-can-cannot-solved-by-Two-Pointers)
 
 ---
 
@@ -35,3 +36,9 @@ By using two pointers, to in place modify array elements.
 
 - There are two arrays, or linked lists
 - They are sorted, or operation in place will not interfere elements after.
+
+### When not use it?
+
+Refer to [this link](https://leetcode.com/problems/subarray-sum-equals-k/discuss/301242/General-summary-of-what-kind-of-problem-can-cannot-solved-by-Two-Pointers)
+
+#TODO: complete this section
\ No newline at end of file