FreeCharge Interview Experience for Senior Software Engineer

Telephone screening
Questions about project and technologies used

F2F:

Round1:
1) Design, develop and implement an elevator problem (only 20 minutes)

Lots of discussion on why the approach is chosen.
Advantages and trade-offs discussed.(For almost an hour)

Round2:
1) All possible permutations of a string.
https://www.w3wiki.net/write-a-c-program-to-print-all-permutations-of-a-given-string/

2) Design,develop and implement Phone directory.
Implement a search algorithm on top of it ..so that it does autocomplete

Eg :
%95% ( Result : 98769512345,9545654312 etc having 95 sequence anywhere)
(Note : Not to use TRIE)

3) Design,develop and implement an OrderGenerating System in distributed servers.
Conditions:
1) No database should be used.
2) The orderID generated should be unique among all servers.

Lots of discussion on various approaches.

4) Difference between equals and hashcode in JAVA

Round3:(Hiring Manager Round)

1) Details about projects in CV.Explanation in detail
2) Check if Binary Tree is BST or not?
https://www.w3wiki.net/a-program-to-check-if-a-binary-tree-is-bst-or-not/