Uber Software Developer Intern Interview Questions and Answers

I prioritize tasks, communicate effectively, and adapt my plans to manage interruptions while maintaining productivity.

• Assess the interruption: Determine its urgency and importance. For example, if a team member needs immediate help, I prioritize that.

• Reorganize my tasks: I create a new plan that accommodates the interruption while ensuring critical deadlines are met.

• Communicate with stakeholders: I inform my team or m...read more

PreOrder traversal without recursion is done using a stack to simulate the function call stack.

• Create an empty stack and push the root node onto it.

• While the stack is not empty, pop a node from the stack and process it.

• Push the right child of the popped node onto the stack if it exists.

• Push the left child of the popped node onto the stack if it exists.

Yes

• Create an empty binary search tree (BST)

• Loop over the unsorted array

• For each element, insert it into the BST using the appropriate insertion logic

• Repeat until all elements are inserted

• The resulting BST will be built from the unsorted array

The question asks to find two elements in an array whose sum is equal to a given number.

• Iterate through the array and for each element, check if the difference between the given number and the current element exists in the array.

• Use a hash set to store the elements as you iterate through the array for efficient lookup.

• Return the pair of elements if found, otherwise return a message indicating no such pair exists.

There are two types of triggers: DML triggers and DDL triggers.

• DML triggers are fired in response to DML (Data Manipulation Language) statements like INSERT, UPDATE, DELETE.

• DDL triggers are fired in response to DDL (Data Definition Language) statements like CREATE, ALTER, DROP.

• Examples: A DML trigger can be used to log changes made to a table, while a DDL trigger can be used to enforce certain rules when a table is alt...read more

Yes, triggers can be used with select statements in SQL.

• Triggers are database objects that are automatically executed in response to certain events, such as insert, update, or delete operations.

• While triggers are commonly used with insert, update, and delete statements, they can also be used with select statements.

• Using triggers with select statements allows you to perform additional actions or validations before or af...read more

Indexing in MySQL improves query performance. There are several types of indexing in MySQL.

• Indexes are used to quickly locate data without scanning the entire table.

• Types of indexing in MySQL include B-tree, hash, full-text, and spatial indexes.

• B-tree indexes are the most common and suitable for most use cases.

• Hash indexes are used for exact match lookups.

• Full-text indexes are used for searching text-based data efficie...read more

Engines in MySQL are the underlying software components that handle storage, indexing, and querying of data.

• MySQL supports multiple storage engines, each with its own strengths and features.

• Some commonly used engines in MySQL are InnoDB, MyISAM, and Memory.

• InnoDB is the default engine in MySQL and provides support for transactions and foreign keys.

• MyISAM is known for its simplicity and speed but lacks transaction suppo...read more

The Singleton pattern ensures a class has only one instance and provides a global point of access to it.

• Restricts instantiation of a class to a single object.

• Useful for managing shared resources, like database connections.

• Implemented using private constructors and static methods.

• Example in Java: public class Singleton { private static Singleton instance; private Singleton() {} public static Singleton getInstance() { if...read more

Yes, a constructor can be private.

• A private constructor can only be accessed within the class itself.

• It is often used in singleton design pattern to restrict object creation.

• Private constructors are also useful for utility classes that only contain static methods.

Print only the leaf nodes of a doubly linked tree.

• Traverse the tree and check if a node has no children and both left and right pointers are null.

• If yes, then it is a leaf node and print it.

• If no, then continue traversing the tree.

• Use recursion to traverse the tree in a depth-first manner.

LRU page replacement algorithm is used to replace the least recently used page in memory with a new page.

• LRU stands for Least Recently Used

• It is a cache eviction algorithm

• It is used to manage memory in operating systems

• It works by keeping track of the pages that are used recently and the ones that are not

• When a new page is to be loaded into memory, the algorithm checks which page has not been used for the longest time ...read more

Reverse m nodes and leave n nodes in a linked list till the end.

• Traverse the linked list till m nodes and reverse them

• Traverse n nodes and continue reversing m nodes

• Repeat the above step till the end of the linked list

• Handle edge cases like m or n being greater than the length of the linked list

Inorder traversal is a way of visiting all nodes in a binary tree by visiting the left subtree, then the root, and then the right subtree.

• Start at the root node

• Traverse the left subtree recursively

• Visit the root node

• Traverse the right subtree recursively

• Repeat until all nodes have been visited

Inorder traversal of a tree without recursion

• Create an empty stack and initialize current node as root

• Push the current node to stack and set current = current.left until current is NULL

• If current is NULL and stack is not empty, pop the top item from stack, print it and set current = popped_item.right

• Repeat step 2 and 3 until stack is empty

Find the triplicate number in an array of duplicates.

• Iterate through the array and keep track of the frequency of each number.

• Return the number that appears three times.

• If no number appears three times, return null.

Explanation of search algorithms with their space and time complexities.

• Linear Search - O(n) time complexity, O(1) space complexity

• Binary Search - O(log n) time complexity, O(1) space complexity

• Jump Search - O(√n) time complexity, O(1) space complexity

• Interpolation Search - O(log log n) time complexity, O(1) space complexity

• Exponential Search - O(log n) time complexity, O(1) space complexity

• Fibonacci Search - O(log n) ...read more

Choosing the right search algorithm depends on data structure, size, and specific requirements like speed or memory usage.

• Binary Search: Efficient for sorted arrays, O(log n) time complexity. Example: Finding a number in a sorted list.

• Linear Search: Simple and works on unsorted arrays, O(n) time complexity. Example: Searching for a name in an unsorted list.

• Depth-First Search (DFS): Suitable for tree/graph traversal, ex...read more

Find the most repeated number in an array of length n with numbers 1-n.

• Create a dictionary to store the count of each number in the array

• Iterate through the array and update the count in the dictionary

• Find the key with the highest count in the dictionary

Change binary tree to make parent node the sum of root nodes

• Traverse the tree in post-order

• For each node, update its value to the sum of its children

• Return the updated root node

Reverse a linkedlist by changing the direction of pointers.

• Iterate through the linkedlist and change the direction of pointers.

• Keep track of previous, current and next nodes.

• Set the next pointer of current node to previous node.

• Move to next node and repeat until end of list is reached.

Rearrange an array of positive and negative numbers with positive numbers on the left and negative numbers on the right.

• Create two empty arrays, one for positive numbers and one for negative numbers

• Loop through the original array and add positive numbers to the positive array and negative numbers to the negative array

• Concatenate the positive and negative arrays to create the rearranged array

String pool is a cache of string literals in memory. Garbage collection frees up memory by removing unused objects.

• String pool is a cache of string literals in memory

• Strings are immutable and can be shared among multiple objects

• Garbage collection removes unused objects to free up memory

• String objects that are no longer referenced are eligible for garbage collection

Synchronizing a HashMap ensures thread safety when multiple threads access it concurrently.

• Use Collections.synchronizedMap(): Wrap the HashMap with this method to create a synchronized version.

• Example: Map<String, String> syncMap = Collections.synchronizedMap(new HashMap<>());

• Use ConcurrentHashMap: This is a thread-safe alternative to HashMap that allows concurrent access.

• Example: ConcurrentHashMap<Strin...read more

Process vs Thread differences and synchronization, deadlock examples

• Process is an instance of a program while thread is a subset of a process

• Processes are independent while threads share the same memory space

• Synchronization is used to coordinate access to shared resources

• Deadlock occurs when two or more threads are blocked waiting for each other to release resources

• Examples of synchronization include mutex, semaphore, ...read more

Design a scalable website to process user requests and send email results asynchronously.

• Use a microservices architecture to handle different processes independently.

• Implement a message queue (e.g., RabbitMQ, Kafka) to manage requests and responses.

• Utilize cloud services (e.g., AWS Lambda) for scalable processing of tasks.

• Send emails using a reliable service (e.g., SendGrid, Amazon SES) to ensure delivery.

• Implement loa...read more