Added a warning note in README

Author: mandliya

README.md

@@ -10,6 +10,8 @@
 
 </center>
 
+**Note: Some of the code here is old and was written when I was learning C++. It might be possible that code is not safe or making wrong assumptions, or never freeing memory on heap etc.Please use with caution. Pull requests are always welcome.**
+
 ### LinkedList Problems
 | Problem | Solution |
 | :------------ | :----------: |