diff --git a/README.md b/README.md
index 2c5b743..db42bf6 100644
--- a/README.md
+++ b/README.md
@@ -38,7 +38,8 @@ This repository contains awesome LeetCode resources to learn Data Structures and
 ## 🚀 Patterns
 - [14 Coding Interview Patterns](https://hackernoon.com/14-patterns-to-ace-any-coding-interview-question-c5bb3357f6ed)
 - [Fast and Slow Pointers Pattern](https://medium.com/@arifimran5/fast-and-slow-pointer-pattern-in-linked-list-43647869ac99)
-- [Prefix Sum Pattern](https://leetcodethehardway.com/tutorials/basic-topics/prefix-sum)
+- [Prefix Sum Pattern](https://leetcode.com/discuss/study-guide/4023666/prefix-sum-questions-to-practice)
+- [String Question Patterns](https://leetcode.com/discuss/study-guide/2001789/Collections-of-Important-String-questions-Pattern)
 - [Sliding Window patterns](https://leetcode.com/problems/frequency-of-the-most-frequent-element/solutions/1175088/C++-Maximum-Sliding-Window-Cheatsheet-Template/)
 - [Two Pointers Patterns](https://leetcode.com/discuss/study-guide/1688903/Solved-all-two-pointers-problems-in-100-days)
 - [Substring Problem Patterns](https://leetcode.com/problems/minimum-window-substring/solutions/26808/Here-is-a-10-line-template-that-can-solve-most-'substring'-problems/)
@@ -52,7 +53,6 @@ This repository contains awesome LeetCode resources to learn Data Structures and
 - [Graph Patterns](https://leetcode.com/discuss/study-guide/655708/Graph-For-Beginners-Problems-or-Pattern-or-Sample-Solutions)
 - [Monotonic Stack Patterns](https://leetcode.com/discuss/study-guide/2347639/A-comprehensive-guide-and-template-for-monotonic-stack-based-problems)
 - [Bit Manipulation Patterns](https://leetcode.com/discuss/study-guide/4282051/all-types-of-patterns-for-bits-manipulations-and-how-to-use-it)
-- [String Question Patterns](https://leetcode.com/discuss/study-guide/2001789/Collections-of-Important-String-questions-Pattern)
 - [DFS + BFS Patterns (1)](https://medium.com/leetcode-patterns/leetcode-pattern-1-bfs-dfs-25-of-the-problems-part-1-519450a84353)
 - [DFS + BFS Patterns (2)](https://medium.com/leetcode-patterns/leetcode-pattern-2-dfs-bfs-25-of-the-problems-part-2-a5b269597f52)
 - [Stock Series Patterns](https://leetcode.com/problems/best-time-to-buy-and-sell-stock-with-transaction-fee/solutions/108870/most-consistent-ways-of-dealing-with-the-series-of-stock-problems/)