StratApps Senior Java Developer Interview Questions and Answers

Round duration - 60 minutes
Round difficulty - Medium

Technical Interview round with questions based on DSA.

Q1. 
Duplicate Integer in Array
Given an array ARR of size N, containing each number between 1 and N-1 at least once, identify the single integer that appears twice.
Input:
The first line contains an integer...read more
Ans. 
Identify the duplicate integer in an array containing numbers between 1 and N-1.
• Iterate through the array and keep track of the frequency of each element using a hashmap.

• Return the element with a frequency greater than 1 as the duplicate integer.

• Ensure the constraints are met and a duplicate number is guaranteed to be present.
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Q2. 
Sum Root to Leaf Numbers
You are given an arbitrary binary tree consisting of N nodes, each associated with an integer value from 1 to 9. Each root-to-leaf path can be considered a number formed by concat...read more
Ans. 
Calculate the total sum of all root to leaf paths in a binary tree formed by concatenating node values.
• Traverse the binary tree from root to leaf nodes, keeping track of the current path sum

• Add the current node value to the path sum and multiply by 10 for each level

• When reaching a leaf node, add the final path sum to the total sum

• Return the total sum modulo (10^9 + 7)
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Q3. 
Topological Sort Problem Statement
You are given a directed acyclic graph (DAG). Your task is to perform topological sorting of the graph and return any valid ordering.
Explanation:
A directed acyclic g...read more
Ans. 
Implement a function to perform topological sorting on a directed acyclic graph (DAG) and return any valid ordering.
• Create a graph data structure to represent the DAG

• Use depth-first search (DFS) to perform topological sorting

• Maintain a visited array to keep track of visited nodes

• Return the ordering of nodes after DFS traversal
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Round duration - 60 minutes
Round difficulty - Easy

Technical interview round with questions based on DSA.

Q1. 
LCA of Binary Tree Problem Statement
You are given a binary tree consisting of distinct integers and two nodes, X and Y. Your task is to find and return the Lowest Common Ancestor (LCA) of these two nodes...read more
Ans. 
Find the Lowest Common Ancestor (LCA) of two nodes in a binary tree.
• Traverse the binary tree to find the paths from the root to nodes X and Y.

• Compare the paths to find the last common node, which is the LCA.

• Handle cases where one node is an ancestor of the other.

• Consider edge cases like when X or Y is the root node.

• Implement a recursive or iterative solution to find the LCA efficiently.
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Q2. 
Rotated Array Minimum Finder
You are provided with a sorted array that has undergone 'K' rotations (the exact value of 'K' is unknown). A rotation involves shifting each element of the array to the right,...read more
Ans. 
Implement a function to find the minimum number in a rotated sorted array efficiently.
• Use binary search to find the minimum element in the rotated array.

• Compare the mid element with the start and end elements to determine which half of the array to search next.

• Continue the binary search until the minimum element is found.
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Q3. 
Maximum Binary Tree Construction Problem
Given an array TREE of 'N' unique integers, construct a maximum binary tree using the following rules:
1. The root of this tree is the maximum number in TREE.
2. T...read more
Ans. 
Construct a maximum binary tree from an array of unique integers following specific rules.
• Find the maximum number in the array to set as the root of the tree.

• Recursively construct the left subtree with elements before the maximum number.

• Recursively construct the right subtree with elements after the maximum number.
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Round duration - 90 minutes
Round difficulty - Medium

It was a cumulative test

Q1. 
Trapping Rainwater Problem Statement
You are given an array ARR of long type, which represents an elevation map where ARR[i] denotes the elevation of the ith bar. Calculate the total amount of rainwater t...read more
Ans. 
Calculate the total amount of rainwater that can be trapped within given elevation map.
• Iterate through the array to find the maximum height on the left and right of each bar.

• Calculate the amount of water that can be trapped above each bar by taking the minimum of the maximum heights on the left and right.

• Sum up the trapped water above each bar to get the total trapped water for the elevation map.
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Round duration - 90 minutes
Round difficulty - Medium

It was sophisticated in nature and a good brain buster.

Q1. 
Candies Distribution Problem Statement
Prateek is a kindergarten teacher with a mission to distribute candies to students based on their performance. Each student must get at least one candy, and if two s...read more
Ans. 
Determine the minimum number of candies needed to distribute to students based on their performance and ratings.
• Iterate through the array of student ratings and assign 1 candy to each student initially.

• Then iterate from left to right and check if the current student's rating is higher than the previous student, if so, assign candies accordingly.

• Similarly, iterate from right to left to handle cases where the current stu...read more
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Round duration - 1 hour
Round difficulty - Medium

Q1. DBMS
It revolved around basic concepts
Ans. 
DBMS is a software system that manages databases and allows users to interact with data stored in them.
• DBMS stands for Database Management System

• It helps in creating, updating, and managing databases

• Examples of DBMS include MySQL, Oracle, SQL Server

• It ensures data integrity, security, and efficient retrieval
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Round duration - 70 minutes
Round difficulty - Hard

It was a great experience

Round duration - 90 minutes
Round difficulty - Medium

It was in the evening at about 7 pm. The test platform was quite user friendly and easy to use.
There were 3 sections in test. One was logical ability, second was english, third was coding 
Questions were of medium difficulty.

Q1. 
Ways To Make Coin Change
Given an infinite supply of coins of varying denominations, determine the total number of ways to make change for a specified value using these coins. If it's not possible to make...read more
Ans. 
The task is to find the total number of ways to make change for a specified value using given denominations.
• Use dynamic programming to solve this problem efficiently.

• Create a 1D array to store the number of ways to make change for each value from 0 to the target value.

• Iterate through the denominations and update the array based on the current denomination.

• The final answer will be the value at the target index of the ar
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Round duration - 30 Minutes
Round difficulty - Medium

It was a 30 minute interview. In which I was provided with questions on data structures and algorithms to check my problem solving skills.

Q1. 
Non-Decreasing Array Problem Statement
Given an integer array ARR of size N, determine if it can be transformed into a non-decreasing array by modifying at most one element.
An array is defined as non-de...read more
Ans. 
Determine if an array can be transformed into a non-decreasing array by modifying at most one element.
• Iterate through the array and check if there are more than one decreasing elements.

• If there is only one decreasing element, check if modifying it can make the array non-decreasing.

• Return true if the array can be made non-decreasing by modifying at most one element, otherwise false.
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Round duration - 40 Minutes
Round difficulty - Medium

In this round , interviewer discussed about my resume. As I had done a internship in sql and database so he asked me questions related to dbms and sql queries.

Q1. About the react node and express js
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