OCI :

Round1 (Problem Solving)
1. Minimum Add to Make Parentheses Valid. https://leetcode.com/problems/minimum-add-to-make-parentheses-valid/
2. Minimum appends required to make a string palindrome.
3. Longest sub-array having sum K.

After Round1 got a call from hr saying, you will be having another 5 rounds.

Round2 (Problem Solving + Design) 
1. Generate all the permutations of a String. : https://leetcode.com/problems/permutations/
2. System Design tiny URL.
3. How DNS works.


Round3 (Bartender)
1. Discussion about current work.
2. Questions related to microservice architecture.
3. Lot of behavioural questions(what are your competencies,biggest achievement,any conflict with team mates/manager etc).
   

Roun4 (Problem Solving)
1. Internal implementation of HashMap, diff between hashMap and TreeMap, how you can use any custom object as a key.
2. You have unlimited number of eggs and n floors. Find number of trials needed to find a floor at which egg wont break.
3. Bulb Switcher : https://leetcode.com/problems/bulb-switcher/
4. Odd even link list : https://leetcode.com/problems/odd-even-linked-list/

Round5 (Technical)
1. Discussion about one of my previous project.
2. Concurrency questions, diff between calling run() and start() ,synchronized keyword,how can you implement threadpool) 
3. How to make your system highly available.
4. Write a program to print all the palindromes in a given String.

Round6 (Hiring Manager)
1. Discussion about my current work and responsibilities.
2. Behavioural questions (biggest technical challange in recent times,why you want to leave current company,Why Oracle etc.)
3. Details about the team,work and the role.


Paytm

Round1 (Problem Solving)

1. Coin change : https://leetcode.com/problems/coin-change/
2. Prefix Search : Given list of words. Get all the words starting from the given prefix
3. https://leetcode.com/problems/search-in-rotated-sorted-array-ii/

Round2(Design)
1. Discussion about current work.
2. Design problem : 
	Search API for a ecommerce website
	There is some data lake where they are populating some unstructured data about all the products. Which gets updated at the end of the day.
	Which contains data about city,productId,number of views,number of purchases for that particular day.
	You have to design a API which can show most popular products of last n days for the given search term in the city.
	Like If you search for shoes it should show most popular products in last n days in the current city.
	You can assume you have one catalog service which gives you all the productIds for given search term.
	How search will work? What will be the structure of the API (Request,Response,Method).


Round3 (JAVA + SPRING + LLD )
1. Discussion about the architecture and design of the previous project.
2. What is dependency injection? How will you implement Spring Dependency Injection? How will you dtetect cyclic dependency?.
3. Internal implementation of HashSet and HashMap.
4. LLD of Parking Lot.