Crown Solutions Senior Java Developer Interview Questions and Answers

Q1. Lookup vs graphlookup in mongodb
Ans. 
Lookup is used to perform a left outer join in MongoDB, while graphlookup is used to perform recursive graph traversal.
• Lookup is used to perform a left outer join between two collections in MongoDB.

• Graphlookup is used to perform recursive graph traversal in a collection that contains graph data.

• Lookup can only perform a single level join, while graphlookup can perform multiple levels of traversal.

• Lookup is faster than
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Q2. Count frequency of each character in string
Ans. 
Use a hashmap to count the frequency of each character in a string.
• Create a hashmap to store characters as keys and their frequencies as values.

• Iterate through the string and update the hashmap accordingly.

• Return the hashmap with character frequencies.
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Q1. Create a rest api all the way from controller to repository using NOTEPAD
Ans. 
Creating a REST API from controller to repository using NOTEPAD
• Create a controller class with mapping annotations for REST endpoints

• Implement service layer to handle business logic and interact with repository

• Define repository interface with methods for data access operations

• Use Spring Boot for easy setup and configuration

• Test API endpoints using tools like Postman
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Q2. Couldnt write custom mongodb query at repository layer in notepad which rejected my candidature.
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40 questions in 20 minutes

Q1. Stones games 2 leetcode
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Q2. Permutations of array
Ans. 
Generate all possible permutations of an array of strings
• Use recursion to generate permutations

• Swap elements to create different permutations

• Base case: when array size is 1, return array as permutation
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Q1. Project discussion
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