Concerto Software Java Developer interview questions

Round 1:- Aptitude Questions Programs: 1. Adding 2 numbers using Recursion. 2. Finding duplicates in an Array. 3. Frequency of Array Elements. Round 2:- In technical Round they asked about OOPS Concept. They asked what is Palindrome. They told to write a program on either string palindrome or number palindrome. They then asked a puzzle. if 3 bulbs are in different room and switches in different room, How to identify which button is for which bulb. Round 3: HR asked about some technical as well as HR Questions.