D.E. Shaw

## Round 0: Online Assessment Type: Online Assessment There were 3 coding problems with individual timers. **Service Pairs Problem**: Given cost, uses pairs for services and a budget, you have to buy a pair of services with the maximum total uses and total cost not exceeding the budget. *Solution*: It is a simple binary search on prefix max; alternatively, segment trees can be used. (25 mins) **DAG Path**: Given a Directed Acyclic Graph (DAG), find the max sum path. This is a standard problem. (35 mins) **Permutation Conversion**: Given an array of integers of length $n$, convert it into a permutation of length $n$ using the minimum number of operations. In one operation, you can choose any index and change the value at that index to anything you want. Among all such permutations that can be obtained, report the lexicographically smallest one. *Solution*: It can be solved greedily very easily. (35 mins) ## Round 1: Technical Type: Technical **Introduction & Projects**: The round started with a brief introduction of the three of us, followed by in-depth questions about the projects mentioned in my resume. I was asked to perform a class diagram analysis for one of them. **DSA Problems**: [Maximum Sum BST in Binary Tree](https://leetcode.com/problems/maximum-sum-bst-in-binary-tree/description/) (Asked to write pseudocode). [Find minimum time to finish all jobs with given constraints](https://www.geeksforgeeks.org/find-minimum-time-to-finish-all-jobs-with-given-constraints/). **Core Subjects**: Questions related to OOPs and DBMS. **Code Debugging**: They showed pieces of code and asked me to point out errors. **Duration**: 1 hour. ## Round 2: Technical + Managerial Type: Technical + Managerial **Introduction & Behavioral**: Started with an introduction and shifted to behavioral questions. **Core Subjects**: Various questions related to OS and OOPs. **DSA Problems**: [Remove Duplicate Letters](https://leetcode.com/problems/remove-duplicate-letters/description/): Solved using a stack. **Availability Window**: Given $n$ people and various time slots during which they are available (in the form of $[l, r]$), report the maximum length of the window where all people are available. *Solution*: I provided a sweep-line solution. **System Design/Real-life Challenge**: How would you maintain a structure that notifies a user about a stock with a price less than what they demanded? Users and stocks are dynamic, and prices change frequently. *Solution*: I suggested binary search on a segment tree, though the interviewers might have been looking for a simpler approach. **Code Output**: Shown segments of code and asked to predict the outputs. ## Experience The interviewers were really friendly and supportive. Even though my interviews went smoothly, I didn’t have many core concepts memorized, so my answers were not very textbook-style. I would recommend preparing the core subjects in depth.