Uber Insight

Rejected

SDE-2

3-5 Years

Jul 29, 2026

Graphs

Data Structures

The interviewer required an optimized solution rather than a brute-force approach.

Proficiency in Disjoint Set Union (DSU), specifically path compression and union by rank, was essential for solving the problem efficiently.

Number of Islands II (Dynamic graph connectivity)

GraphsDSU

Dynamic ProgrammingTrees

The problem was a variation of the Optimal Binary Search Tree (OBST) problem.

The candidate needed to identify the underlying DP structure to minimize the weighted cost of the tree.

The interviewer evaluated the ability to translate a business-logic cost formula into a mathematical DP formulation.

Construct an Optimal Binary Search Tree given words and costs to minimize weighted depth.

Dynamic ProgrammingTrees

Data StructuresAPI DesignTime Complexity

The candidate over-engineered the solution by focusing on LLD (Low-Level Design) patterns instead of meeting the O(1) time complexity constraint.

The interviewer prioritized the correct choice of data structures (HashMaps/Reverse mappings) over clean code aesthetics.

A major lesson was to solve for constraints first and refactor only if time permits.

Design APIs for employee-manager relationships with O(1) operations for get, changeManager, and addEmployee.

Data StructuresAPI Design

System DesignConcurrencyCaching

The candidate incorrectly applied the CAP theorem to a single-node system where it was not relevant.

The interviewer expected a focus on locking strategies, read-write contention, and eviction mechanics rather than distributed systems theory.

The candidate learned to clarify the scope of the system (distributed vs. single-node) before applying high-level architectural patterns.

Design an in-memory cache with support for eviction strategies and concurrency.

System DesignCaching

Time management under pressure is more critical than complex logic.
Clarity and correctness take precedence over code beauty.
Ensure the scope of the system design problem is understood before applying theoretical frameworks like CAP.
Treat interview failures as opportunities to identify gaps in technical depth.

Practice DSU, DP, and classic CS problems.
Be ruthless about time complexity requirements.
Avoid over-engineering in coding rounds; prioritize functionality over clean code.
Think out loud and justify every decision made during the design process.