You are a Backend Engineer at DoorDash and notice that your service can no longer keep up with traffic.To handle the increased load, the team decides to scale horizontally by adding more pods running your service. A colleague implemented a traffic router that distributes requests to pods using a round-robin algorithm. However, the implementation does…

You are given a binary tree where every node contains: Given two nodes in this tree, return their Lowest Common Ancestor (LCA). Below is the structure of the tree: You will be given two input nodes, and your task is to return the node that is their lowest shared ancestor in the tree. Example Input…

You are given an array of integers. Your task is to return the k most frequent elements from the array.If two or more elements share the same frequency, you may return them in any order.If the number of unique elements is less than k, return all unique values. Examples This DoorDash VO interview question evaluates…

You are given a sorted array of 10 elements.Given a target number, find two distinct elements in the array whose sum equals the target. Example array Input: a target value T.Output: any pair (x, y) from Arr such that x + y = T (or report that no such pair exists). Classic two-sum in a…

Given an array of integers, the cost to change an element is the absolute difference between its initial value and its new value.For example, if an element is initially 10, it can be changed to 7 or 13 for a cost of 3. Task. Determine the minimum total cost to make the array sorted along…

We have a list of tasks. Each task can depend on other tasks.If task A depends on task B, then B should run before A. Implement the method getTaskWithDependencies such that it returns a list of task names in the correct order. Example:If we want to execute task “application A”, the method should return: The…

CoderPad provides a basic SQL sandbox with the following schema.You can also use commands like show tables and desc … Group employees_projects by employee_id and filter with HAVING COUNT(DISTINCT project_id) > 1. Use DISTINCT to guard against duplicate links; join employees only if names are needed. Add indexes on employee_id/project_id (or a composite) for performance….

Robinhood is famous for its referral program. It’s exciting to see users spreading the word across their friends and family. One thing that is interesting about the program is the network effect it creates. We would like to build a dashboard to track the status of the program. Specifically, we would like to learn about…

Problem Statement: Build a service/system that can support defining and running jobs on a schedule. Requirements: Summary (what to design & key choices) Goal: A horizontally scalable, highly reliable job orchestration service (cron-as-a-service). Core components Key APIs Data model (simplified) Scheduling strategy Failure & SLA handling Scaling The VOprep team has long accompanied candidates through various major…

Input (stdin)An order message is a request to trade shares: New fields: Order rules ✅ Output (stdout) After receiving an order at time T, emit prints: Following constraints: ✅ Example Output Explanation: ✅ Summary This problem simulates an execution algorithm constrained by: ✅ Trailing-minute external traded volume✅ Participation rate limits (PR)✅ Expiration of orders✅ Partial…

Input (stdin)The program reads the input line by line. Each line must be one of the following message types: • A print represents a trade that took place on the exchange: • A volume check is a request to report the total traded quantities of a security in the preceding minute, as well as its…

You have been tasked with creating an exchange where traders can buy and sell Sea Shells. The program reads incoming orders and emits trades. Input (stdin) – the input is a stream of limit orders. Each line is a separate order identified by its line number (starting at 1), with space-delimited fields: Examples: Processing orders…

A Kac ring is a dynamical system defined as follows: Part 1: Implement a Kac ring with the following interface: Brief summary: Simulate a circular system where balls move one step each tick and flip color only when leaving a marked slot. Build an object with step() and an O(1) color() that returns (white−black)/N(white –…

The program reads the input line by line from stdin.Each line is exactly one of the following message types: Fields (space-delimited): An order is: Output For each volume-check for security S at time T, emit exactly one line: Where: A volume-check response must be printed immediately before reading the next input line. For each order…

Ski season is approaching! You work at a ski resort and must ensure the slopes are fully covered with snow. You have a slope with indices from 0…N, and a collection of snow-making machines installed along the slope.Each machine is a tuple (index, range) meaning the machine sits at index and can cover the slope…

Problem (verbatim) Design a data structure that supports insert, delete, search, and getRandom in constant time. Use a dynamic array + hash map (value → index). The VOprep team has long accompanied candidates through various major company OAs and VOs, including Tiktok, Google, Amazon, Citadel, SIG, providing real-time voice assistance, remote practice, and interview pacing reminders to…

Given an array of positive integers nums and an integer k,return true if nums has a continuous subarray whose sum equals k. Examples: Since all numbers are positive, we can use a sliding window: This works in O(n) because the two pointers only move forward. The VOprep team has long accompanied candidates through various major company OAs…

You are given a string s.You can convert s to a palindrome by adding characters in front of it.Return the shortest palindrome you can form by performing this transformation. Input:s = “aacecaaa” Output:”aaacecaaa” The task is to create the shortest palindrome by adding characters only to the front of the given string. Main idea: Optimal…

Given a string s, return true if it is a palindrome, or false otherwise. Input:s = “aba” Output:true This problem checks whether a string is a palindrome, meaning it reads the same forward and backward. Typical approach: Runs in O(n) time and O(1) space (two-pointer approach). The VOprep team has long accompanied candidates through various major company…

A unique character is one that appears only once in a string.Given a string consisting of lowercase English letters only, return the index of the first occurrence of a unique character in the string using 1-based indexing.If the string does not contain any unique character, return -1. Example:s = “statistics”The unique characters are [a, c],…