Daily practice

Questions

Unique DSA problems from real interviews. No solutions — think through them yourself and build genuine problem-solving intuition.

78 questions

Hard2026-10-08

Questions

Implement shared_ptr from Scratch

Reverse a Stack Recursively Without Extra Data Structure

Design a Thread-Safe Producer-Consumer Queue

Rat's Safest Path — Maximize Distance from the Cat

Minimum GPU Memory to Train All Models in K Days

Maximize Array Sum After Exactly K Sign Flips

Longest Substring Transformable Within a Cost Budget

Safe Microservice Deployment Order (with Cycle Detection)

Group Fraud Accounts by Shared Signals (Union-Find)

Find the Lowest Common Manager of Two Employees

Ad Budget Pacing - Find the Cutoff Spend Per Campaign

Kth Highest Score in a Live Gaming Leaderboard

Merge Overlapping Feature Flag Rollout Windows

Search Autocomplete with Top-3 Ranked Suggestions

Find the Corrupted and Missing Shard IDs

Longest Valid Route Through an API Gateway

My Calendar I — Book Events Without Double Booking

Design a Chat Application like ChatGPT

First Unique Number in a Stream

Design a Hit Counter (with Per-Element Counts)

Coin Game — Pick from Either Corner (Optimal Play)

100 Lockers — The Toggle Problem

House Robber II — Circular Arrangement

Design a Rate Limiter (System Design)

Design a Browser Tab Handler

Second Rightmost Node in a Binary Tree

Search in Rotated Sorted Array

Design an LRU Cache

Rotate Array by K Steps

Number of Islands (Making an Island)

Minimum Cost Path in Grid with Cell Flipping

Design Device with Composable Capabilities (LLD)

Design a Bus Booking System (like RedBus)

Design a Max Stack

Heaters — Minimum Radius to Warm All Houses

Design JIRA — Handling Concurrent Edits to the Same Ticket

Design Google Docs — Real-Time Collaborative Editing

Add Two Large Numbers Represented as Strings

Design a Premium Cab Hailing Service (LLD)

Schedule Maximum Rakhi Celebrations

Design a Stock Price Change Alert System

Find Median from a Data Stream

Robot Path in Grid with Charging Stations (Multi-Priority Optimization)

Design Top-N Leaderboard with Rolling Time Windows

Friend Suggestions Based on Mutual Connections

Max Consecutive Ones III — With Circular Array Follow-up

Design a Large-Scale Payment Processing Platform

Find All Anagrams of a Pattern in a String

Convert Sorted Doubly Linked List to Balanced BST (In-Place)

Top K Frequent Numbers from a Continuous Stream

Multi-Source BFS in a Complex Scenario

Implement Advanced Debounce with Leading Edge and Cancel

Shortest Subarray with Sum at Least K (with Negatives)

Design and Implement a Distributed Job Scheduler

Design Microsoft Word — LLD with Undo/Redo

Implement Basic Arithmetic Without Inbuilt Operators

Asteroid Collisions

Implement Browser History Navigation

Design an Auction Platform — Real-time Bidding System

Maximum of Every Sliding Window of Size K

Basic Calculator with OOP Extension

Data Migration Lag Verifier — Alert on Replication Delay

Find Distance Between Two Nodes in a Binary Tree

Group Buddy Strings by Cyclic Distance

Rotten Oranges — Multi-source BFS on Grid

Design a Stack with O(1) Push, Pop, GetMiddle, and GetTop

Design a Versioned Datastore with PUT and GET

DP with Binary Search Optimization

Modified Union-Find with Weighted Graph Components

Trie + HashMap Based String Pattern Matching

Design a Tooltip Using Only HTML/CSS — No JavaScript

Implement Array.prototype.myFlat(depth)

Rate Limiter — Count Dropped Requests

Stock Span Problem — All Three Variants

Remove Duplicates from Sorted Array — Allow at Most K

Run-Length Encoding with Consecutive Count

Bottom View of a Binary Tree

Design a Remote Browser Isolation System