Qualcomm Senior Java Developer Interview Questions and Answers for Freshers

Round duration - 30 minutes
Round difficulty - Easy

Q1. How do you search for a node in a linked list?
Ans. 
To search for a node in a linked list, iterate through the list and compare each node's value with the target value.
• Start at the head of the linked list

• Iterate through each node by following the 'next' pointer

• Compare the value of each node with the target value

• Return the node if found, otherwise return null
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Q2. How do you detect a loop in a linked list?
Ans. 
To detect a loop in a linked list, we can use Floyd's Cycle Detection Algorithm.
• Initialize two pointers, slow and fast, at the head of the linked list.

• Move slow pointer by one step and fast pointer by two steps.

• If there is a loop, the two pointers will eventually meet.

• Alternatively, we can use a hash set to store visited nodes and check for duplicates.
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Q3. Implement a stack using a singly linked list.
Ans. 
Implement a stack using a singly linked list
• Create a Node class with data and next pointer

• Create a Stack class with top pointer pointing to the top of the stack

• Implement push, pop, and peek operations by manipulating the linked list

• Example: Node class - Node { int data; Node next; }
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Round duration - 40 minutes
Round difficulty - Easy

Q1. What is the top view of a binary tree?
Ans. 
The top view of a binary tree shows the nodes visible from the top when looking down from the root node.
• The top view of a binary tree is the set of nodes visible from the top when looking down from the root node.

• Nodes at the same horizontal distance from the root are considered at the same level in the top view.

• If multiple nodes are at the same horizontal distance, only the topmost node at that level is included in the...read more
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Q2. Explain the process of deleting a node from a linked list, covering all possible cases.
Ans. 
Deleting a node from a linked list involves updating pointers to maintain the list's integrity.
• Identify the node to be deleted by traversing the list

• Update the previous node's next pointer to skip the node to be deleted

• Free the memory allocated to the node to be deleted
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Round duration - 75 minutes
Round difficulty - Medium

This was an online coding round where I had 2 questions to solve under 75 minutes. Both the coding questions were related to DP and were of Medium to Hard level of difficulty.

Q1. 
Longest Common Prime Subsequence Problem Statement
Imagine Ninja is tackling a puzzle during his long summer vacation. He has two arrays of integers, each with lengths 'N' and 'M'. Ninja's task is to dete...read more
Ans. 
Find the length of the longest subsequence common to two arrays consisting only of prime numbers.
• Iterate through both arrays to find prime numbers

• Use dynamic programming to find the longest common subsequence

• Consider edge cases like empty arrays or no common prime numbers
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Q2. 
Maximum Sum Problem Statement
You are given an array ARR of N integers. Your task is to perform operations on this array until it becomes empty, and maximize the sum of selected elements. In each operatio...read more
Ans. 
Given an array, select elements to maximize sum by removing adjacent elements. Return the maximum sum.
• Iterate through the array and keep track of the frequency of each element.

• Select the element with the highest frequency first, then remove adjacent elements.

• Repeat the process until the array becomes empty and calculate the sum of selected elements.
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Round duration - 60 minutes
Round difficulty - Medium

This round had 2 Algorithmic questions wherein I was supposed to code both the problems after discussing their approaches and respective time and space complexities . After that , I was grilled on some OOPS concepts related to C++.

Q1. 
Cycle Detection in a Linked List
Your task is to determine if a given Singly Linked List of integers forms a cycle.
Explanation: A cycle in a linked list occurs when there is a node in the list that conn...read more
Ans. 
Detect if a given singly linked list of integers forms a cycle.
• Use Floyd's Tortoise and Hare algorithm to detect cycle in linked list

• Maintain two pointers, one moving at double the speed of the other

• If they meet at some point, there is a cycle in the linked list
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Q2. 
Check If Preorder Traversal Is Valid
Determine whether a given array ARR of positive integers is a valid Preorder Traversal of a Binary Search Tree (BST).
A binary search tree (BST) is a tree structure w...read more
Ans. 
Check if a given array of positive integers is a valid Preorder Traversal of a Binary Search Tree (BST).
• Create a stack to keep track of nodes.

• Iterate through the array and compare each element with the top of the stack.

• If the current element is less than the top of the stack, push it onto the stack.

• If the current element is greater than the top of the stack, pop elements from the stack until a greater element is found ...read more
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Q3. What are Vtable and VPTR in C++?
Ans. 
Vtable and VPTR are used in C++ for implementing polymorphism through virtual functions.
• Vtable (Virtual Table) is a table of function pointers used to implement dynamic dispatch for virtual functions.

• VPTR (Virtual Pointer) is a pointer that points to the Vtable of an object.

• Vtable is created by the compiler for each class that has virtual functions.

• VPTR is added as a hidden member in each object of a class with virtual...read more
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Q4. What are friend functions in C++?
Ans. 
Friend functions in C++ are functions that are not members of a class but have access to its private and protected members.
• Friend functions are declared inside a class with the keyword 'friend'.

• They can access private and protected members of the class.

• They are not member functions of the class, but have the same access rights as member functions.

• Friend functions are useful when you want to allow a function external to
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Round duration - 60 minutes
Round difficulty - Medium

This was also a DS/Algo round where I was given 2 questions to solve and I was expected to come up with the optimal approach as far as possible. I solved both the questions with the optimal time and space complexities and then I was asked some more questions related to DBMS towards the end of the interview.

Q1. 
Top View of a Binary Tree
You are given a binary tree. Your task is to print the Top View of the Binary Tree, displaying the nodes from left to right order.
Input:
The first line contains an integer 't'...read more
Ans. 
The task is to print the Top View of a Binary Tree from left to right order.
• Use a map to store the horizontal distance of each node from the root.

• Perform a level order traversal of the tree and keep track of the horizontal distance of each node.

• Print the nodes in the map in ascending order of their horizontal distance.

• Handle the case where multiple nodes have the same horizontal distance by printing the one that appear
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Q2. 
Count Palindromic Substrings Problem Statement
Given a string STR, determine the total number of palindromic substrings within STR.
Input:
The first line contains an integer 't' representing the number ...read more
Ans. 
Count the total number of palindromic substrings in a given string.
• Iterate through each character in the string and expand around it to find palindromic substrings.

• Use dynamic programming to store previously calculated palindromic substrings.

• Consider both odd and even length palindromes while counting.

• Example: For input 'abbc', palindromic substrings are ['a', 'b', 'b', 'c', 'bb']. Total count is 5.
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Q3. What is the difference between the DELETE and TRUNCATE commands in a DBMS?
Ans. 
DELETE removes specific rows from a table, while TRUNCATE removes all rows and resets auto-increment values.
• DELETE is a DML command, while TRUNCATE is a DDL command.

• DELETE can be rolled back, while TRUNCATE cannot be rolled back.

• DELETE triggers delete triggers, while TRUNCATE does not trigger any triggers.

• DELETE is slower as it maintains logs, while TRUNCATE is faster as it does not maintain logs.

• Example: DELETE FROM t
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Q4. What is meant by normalization and denormalization?
Ans. 
Normalization is the process of organizing data in a database to reduce redundancy and improve data integrity, while denormalization is the process of intentionally introducing redundancy to improve performance.
• Normalization involves breaking down a table into smaller tables and defining relationships between them to reduce redundancy and dependency.

• Denormalization involves combining tables and duplicating data to impr...read more
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Q1. What was the major issues attending & how solve it
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Q1. Be strong your technical knowledge
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Q1. Need communication skill
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Q1. Question will be on 7qc tools, fmea, kaizen, 5s, pokayoke
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Q2. What is error proofing
Ans. 
Error proofing is a method of designing processes or systems to prevent errors from occurring.
• Error proofing involves identifying potential errors and implementing measures to prevent them.

• Examples of error proofing include using checklists, automation, and visual cues to guide correct actions.

• Error proofing helps improve quality, reduce defects, and increase efficiency in operations.
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Q3. What is quality management system
Ans. 
Quality management system is a set of policies, processes, and procedures required for planning and execution in the core business area of an organization.
• It involves defining quality policies and objectives

• Implementing processes to ensure quality standards are met

• Monitoring and measuring performance

• Continual improvement through corrective actions and audits
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Q1. What we given input from our resume, related questions asking
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