Oracle Full Stack Developer Interview Questions, Process, and Tips

Delete nodes from linkedList if their value matches a certain condition

Q1. Js advanced concepts
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Q2. Java concurrency
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Q3. Design patterns
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Q1. Implement few design patterns
Ans. 
Implementing design patterns in software development
• Singleton pattern ensures a class has only one instance and provides a global point of access to it

• Factory pattern creates objects without specifying the exact class of object that will be created

• Observer pattern defines a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated
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Q2. Questions of microservice architecture
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Q3. Java 8 tricky coding questions
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Round duration - 50 Minutes
Round difficulty - Medium

It was the screening round he asked me 2 questions 
First one is easy and other one is medium type

Q1. Two Sum
You are given an array of integers 'ARR' of length 'N' and an integer Target. Your task is to return all pairs of elements such that they add up to Target.
Note:
We cannot use th...read more
Ans. Hashing Solution
• We can store the frequency of every element in the array in a hashmap.
• We will loop over every index i, and check the frequency of (Target - ARR[i]) is the hashmap:
  • If (Target - ARR[i]) is equal to ARR[i], we will check if frequency of ARR[i] . If it is greater than 1 then we will decrease the frequency of ARR[i] by 2 and add a pair (ARR[i] , ARR[i]) to our answer.
  • Else, if the frequency of ARR[i] and Targ...read more
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Q2. Root to Leaf Path
Ninja is having a good time in solving new questions of Binary Trees from Code Studio. He is now encountered with a question having statement as "You are given a binary tree consisti...read more
Ans. DFSSpace Complexity: O(1)Explanation: Time Complexity: O(1)Explanation:
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Round duration - 45 Minutes
Round difficulty - Easy

This is the first round in the loop interviews. Are you familiar with Javascript. Why do we use js. How do you use js to change the value of a textbox.

Q1. Validate BST
Given a binary tree with N number of nodes, check if that input tree is BST (Binary Search Tree) or not. If yes, return true, return false otherwise.
A binary search tree (BST) is a binary t...read more
Ans. Approach 1
• For each node, store the minimum and maximum value allowed for that node.
• Initially, for the root node as all the integer values are allowed, the minimum value would be -10^9 and the maximum value should be 10^9. Here we can also use built-in INT_MIN and INT_MAX constants.
• If the value of that node is not in the bounded range of minimum and maximum value, then return false.
• For the left subtree of a node with da...read more
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Q2. Construct Tree From Preorder Traversal
Given an array ‘pre[]’ of ‘n’ elements that represent Preorder traversal of a spacial binary tree where every node has either 0 or 2 children. Also Given a boolean ar...read more
Ans. Recursive Approach
• The idea is to construct the tree node by node.
• Take the first element of the ‘pre[]’ array. Now it is guaranteed that this will be the root node because of the definition of pre-order traversal.
• Now for any node, if ‘isLeaf’ is true it means that it is a leaf node. In this case, we create the node and return it.
• Otherwise, since the binary tree has no children or 2 children, we recursively call the func...read more
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Round duration - 45 minutes
Round difficulty - Easy

It was the team fit round

Q1. Basic HR Question
He asked me questions related to previous work in depth, projects I have worked on.
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Round duration - 45 Minutes
Round difficulty - Medium

4tn round in the loop, he asked me to design a game. He focused both on backend and frontend.
..

Q1. Bursting Balloons
You are given an array 'ARR' of N integers. Each integer represents the height of a balloon. So, there are N balloons lined up.
Your aim is to destroy all these balloons. Now, a...read more
Ans. Using hashmap
We can see here that balloons need to be destroyed in a minimum number of arrows so we need to reuse the arrows, also it’s clear that we need a new arrow for every balloon which is not getting destroyed by any previous arrow.
So we can solve this problem greedily by adding a new arrow for every balloon which is not getting destroyed by existing arrows.
• We will use a map data structure that will store the hei...read more
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Round duration - 45 Minutes
Round difficulty - Medium

Another problem solving round

Q1. Triplets with Given Sum
You are given an array/list ARR consisting of N integers. Your task is to find all the distinct triplets present in the array which adds up to a given number K.
An array is said t...read more
Ans. Brute Force
• The most trivial approach would be to find all triplets of the array and count all such triplets whose ‘SUM’ = 'K'.
• We can find the answer using three nested loops for three different indexes and check if the values at those indexes sum up to 'K'.
• Create a set  to keep the track of triplets we have visited. Run first loop from i = 0 to i = ‘N’ - 3, second loop from j = i + 1 to j = ‘N’ - 2 and third loop ...read more
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