Fix Two Sum README

Author: thanthtooaung-coding

README.md

@@ -13,20 +13,24 @@ Each problem has its own directory containing:
 | # | Title | Difficulty | Solution | Topics |
 |---|-------|------------|----------|---------|
 | 1 | [Two Sum](Two%20Sum) | Easy | [Java](Two%20Sum/Solution.java) | Array, Hash Table |
+| 4 | [Median of Two Sorted Arrays](Median%20of%20Two%20Sorted%20Arrays) | Hard | [Java](Median%20of%20Two%20Sorted%20Arrays/Solution.java) | Array, Binary Search, Divide and Conquer |
 | 2924 | [Find Champion II](Find%20Champion%20II) | Medium | [Java](Find%20Champion%20II/Solution.java) | Graph |
 
 ## Categories
 
 ### By Difficulty
 - Easy: 1
 - Medium: 1
-- Hard: 0
+- Hard: 1
 
 ### By Topics
 - Array Problems
   - [Two Sum](Two%20Sum)
+  - [Median of Two Sorted Arrays](Median%20of%20Two%20Sorted%20Arrays)
 - Hash Table Problems
   - [Two Sum](Two%20Sum)
+- Binary Search Problems
+  - [Median of Two Sorted Arrays](Median%20of%20Two%20Sorted%20Arrays)
 - Graph Problems
   - [Find Champion II](Find%20Champion%20II)