Topic Questions

Browse questions under selected topic.

Bank Balance

Easy
9 views 24 Jan 2026
You have a bank account with starting balance B. Then q commands: DEP x, WIT x (withdraw, but if not enough keep same). Output final balance....
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Simple Counter

Easy
11 views 24 Jan 2026
You have q commands: INC, DEC. Create Counter class. DEC cannot go below 0. Output final value....
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Student Average

Easy
9 views 24 Jan 2026
You get {x}. Create Student class with method avg(). Output average with 2 decimals....
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Point Distance

Easy
9 views 24 Jan 2026
You're given {x}. Create Point class with method dist0() giving distance from origin. Output with 3 decimals....
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Book Thick Check

Easy
8 views 24 Jan 2026
Title (no spaces) and pages are provided. Create Book class with method thick() that returns YES if pages>300 else NO....
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Temperature Convert Class

Easy
8 views 24 Jan 2026
Celsius value is provided. Create Temperature class with method to_f(). Output Fahrenheit with 2 decimals....
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Car Fuel Check

Easy
11 views 24 Jan 2026
Distance d, mileage m (km per litre) and fuel f are provided. Create Car class can_reach(d) returns YES if fuel enough else NO....
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Stack Class

Easy
8 views 24 Jan 2026
You will receive q commands: PUSH x, POP, TOP. Create Stack class and for TOP output value or EMPTY....
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Inventory Total Cost

Medium
9 views 24 Jan 2026
We have {x}. Create Item class with total() method. Output grand total cost....
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Sort Circles By Area (OOP)

Medium
8 views 24 Jan 2026
Input provides {x}. Create Circle class with area() and sort circles by area ascending. Output sorted radii....
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Time Add Seconds

Medium
9 views 24 Jan 2026
Time hh mm ss and extra seconds x are provided. Create Time class add(x) and output new time in HH:MM:SS (24h)....
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Employee Yearly Salary

Medium
8 views 24 Jan 2026
Given {x}, Create Employee class yearly() to return yearly salary with bonus included. Output as integer....
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Fraction Add

Medium
10 views 24 Jan 2026
You get {x}. Create Fraction class that reduces and supports add. Output result as p q reduced....
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Matrix Sum

Medium
9 views 24 Jan 2026
Given {x}, Create Matrix class with add method. Output resulting matrix....
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Task Tracker

Medium
8 views 24 Jan 2026
You will receive q commands: ADD name, DONE name, COUNT. Create TaskTracker class. COUNT prints how many tasks are pending....
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Group Scores

Medium
10 views 24 Jan 2026
We have {x}. Create Player class and group by name summing scores. Output names sorted with total score....
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Shopping Cart

Medium
10 views 24 Jan 2026
You will receive q commands: ADD item price, REMOVE item, TOTAL. Create Cart class. TOTAL prints sum of prices of current items....
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Queue With Two Stacks

Medium
9 views 24 Jan 2026
You will receive q commands: ENQ x, DEQ, FRONT. Create Queue class using two stacks. FRONT prints front value or EMPTY....
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URL Parts

Medium
9 views 24 Jan 2026
One URL string like domain/path is provided (no spaces). Create URL class with domain() and path() methods. If no '/', path is EMPTY....
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Password Rules

Medium
10 views 24 Jan 2026
You're given {x}. Create Validator class ok() that checks: length>=8, has at least one digit, one uppercase, one lowercase. Output YES or NO....
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Polynomial Evaluate

Medium
9 views 24 Jan 2026
Given {x}, Create Polynomial class eval(x). Output value....
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Min Stack Class

Hard
9 views 24 Jan 2026
You will receive q commands: PUSH x, POP, MIN. Create MinStack class and for MIN output current minimum or EMPTY....
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LRU Cache Class

Hard
8 views 24 Jan 2026
Cache capacity cap is provided and q commands: PUT k v, GET k. Implement LRUCache class. For GET output value or -1....
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Graph Shortest Path Class (OOP)

Hard
8 views 24 Jan 2026
We have {x}. Create Graph class with bfs(s,t) method. Output shortest distance or -1....
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Calendar Conflicts

Hard
11 views 24 Jan 2026
You're given {x}. Create Calendar class add(start,end) returns YES if added else NO (conflict if overlap). Output results for each add....
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Nested Store Class

Hard
9 views 24 Jan 2026
You will receive q commands: SET path value, GET path. Path is dot separated. Create Store class to handle. For GET output value or NOT FOUND....
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Sparse Vector Dot Product

Hard
11 views 24 Jan 2026
Two sparse vectors are provided as list of index:value pairs. Build SparseVector class with dot(other). Output dot product....
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Complex Numbers Sum and Product

Medium
7 views 24 Jan 2026
Consider {x}. Create Complex class with add and mul. Output sum then product as 'x y' for real and imag....
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Email Normalizer

Medium
8 views 24 Jan 2026
You get {x}. Create Email class that normalizes (lowercase, trim spaces). Output count of unique normalized emails....
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Connectivity Queries (DSU) (OOP)

Hard
10 views 24 Jan 2026
Input provides {x}. Make DSU class with find and union. Queries: UNION u v, ASK u v. For ASK output YES if connected else NO....
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Trie Prefix Counter (OOP)

Hard
10 views 24 Jan 2026
You're given {x}. Create Trie class. For COUNT output how many added words have this prefix....
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Median Finder Class (OOP)

Hard
8 views 24 Jan 2026
You will receive q commands: ADD x or MEDIAN. Create MedianFinder class using two heaps. For MEDIAN output lower median (floor for even count)....
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Segment Tree Range Minimum (OOP)

Hard
10 views 24 Jan 2026
You get {x}. Build SegmentTree class with update(i,x) and query(l,r) returning minimum. Output query answers....
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Classroom Register (Student CRUD)

Medium
8 views 24 Jan 2026
Maintain a student register. Process q commands: ADD id name, DEL id, GET id, COUNT. Print output for each GET and COUNT....
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Bank Account Ledger

Medium
9 views 24 Jan 2026
Simulate one bank account. Start balance = 0. Commands: DEPOSIT x, WITHDRAW x, FEE x. WITHDRAW fails if balance...
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Shape Area Total

Easy
9 views 24 Jan 2026
You will get q shapes. Each line: RECT w h, CIRC r, or SQR a. Print total area with 2 decimals....
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LRU Cache Simulator

Hard
9 views 24 Jan 2026
Implement an LRU cache of capacity C. You will get q operations: GET key and PUT key value. For each GET print value or -1....
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Event Subscriptions (Topic Bus)

Hard
11 views 24 Jan 2026
Commands: SUB user topic, UNSUB user topic, PUB topic msg(no spaces). For each PUB print how many users receive the message....
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Top Customers by Spend

Easy
6 views 24 Jan 2026
Tables: Orders(order_id, customer_id, total_amount, created_at). Return customer_id and total spend, sorted by spend desc....
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Employees Without Manager

Easy
8 views 24 Jan 2026
Table: Employees(emp_id, name, manager_id). Find employees who have no manager....
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Second Highest Salary

Easy
5 views 24 Jan 2026
Table: Employees(emp_id, salary). Return the second highest distinct salary. If it does not exist, return NULL....
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Daily Active Users

Easy
9 views 24 Jan 2026
Table: Logins(user_id, login_time). Return date and number of distinct users per date....
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Orders With Missing Customers

Medium
6 views 24 Jan 2026
Tables: Orders(order_id, customer_id), Customers(customer_id). List orders whose customer_id does not exist in Customers....
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Products Never Sold

Medium
5 views 24 Jan 2026
Tables: Products(product_id, name), OrderItems(order_id, product_id). Find products that never appear in OrderItems....
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Nth Highest Salary (Parameter N)

Hard
5 views 24 Jan 2026
Table: Employees(emp_id, salary). Write a query pattern to get the Nth highest distinct salary (assume N is given)....
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Users With 3 Consecutive Logins

Hard
8 views 24 Jan 2026
Table: Logins(user_id, day). day is a date. Find users who logged in on 3 consecutive days....
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Window Function Practice #9

Hard
4 views 24 Jan 2026
Table: Scores(user_id, score, created_at). Return each row with the rank of score within the same day....
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Join Practice #10

Easy
5 views 24 Jan 2026
Tables: A(id, val), B(id, val). Return ids present in both tables....
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Aggregation Practice #11

Medium
4 views 24 Jan 2026
Table: Sales(store_id, amount). Return store_id and average amount, only stores with at least 5 rows....
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Window Function Practice #12

Hard
4 views 24 Jan 2026
Table: Scores(user_id, score, created_at). Return each row with the rank of score within the same day....
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Join Practice #13

Easy
5 views 24 Jan 2026
Tables: A(id, val), B(id, val). Return ids present in both tables....
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Aggregation Practice #14

Medium
4 views 24 Jan 2026
Table: Sales(store_id, amount). Return store_id and average amount, only stores with at least 5 rows....
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Window Function Practice #15

Hard
4 views 24 Jan 2026
Table: Scores(user_id, score, created_at). Return each row with the rank of score within the same day....
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Join Practice #16

Easy
4 views 24 Jan 2026
Tables: A(id, val), B(id, val). Return ids present in both tables....
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Aggregation Practice #17

Medium
4 views 24 Jan 2026
Table: Sales(store_id, amount). Return store_id and average amount, only stores with at least 5 rows....
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Window Function Practice #18

Hard
4 views 24 Jan 2026
Table: Scores(user_id, score, created_at). Return each row with the rank of score within the same day....
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Join Practice #19

Easy
4 views 24 Jan 2026
Tables: A(id, val), B(id, val). Return ids present in both tables....
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Aggregation Practice #20

Medium
4 views 24 Jan 2026
Table: Sales(store_id, amount). Return store_id and average amount, only stores with at least 5 rows....
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Window Function Practice #21

Hard
4 views 24 Jan 2026
Table: Scores(user_id, score, created_at). Return each row with the rank of score within the same day....
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Join Practice #22

Easy
5 views 24 Jan 2026
Tables: A(id, val), B(id, val). Return ids present in both tables....
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Aggregation Practice #23

Medium
6 views 24 Jan 2026
Table: Sales(store_id, amount). Return store_id and average amount, only stores with at least 5 rows....
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Window Function Practice #24

Hard
4 views 24 Jan 2026
Table: Scores(user_id, score, created_at). Return each row with the rank of score within the same day....
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Join Practice #25

Easy
4 views 24 Jan 2026
Tables: A(id, val), B(id, val). Return ids present in both tables....
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Aggregation Practice #26

Medium
4 views 24 Jan 2026
Table: Sales(store_id, amount). Return store_id and average amount, only stores with at least 5 rows....
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Window Function Practice #27

Hard
8 views 24 Jan 2026
Table: Scores(user_id, score, created_at). Return each row with the rank of score within the same day....
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Join Practice #28

Easy
6 views 24 Jan 2026
Tables: A(id, val), B(id, val). Return ids present in both tables....
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Aggregation Practice #29

Medium
4 views 24 Jan 2026
Table: Sales(store_id, amount). Return store_id and average amount, only stores with at least 5 rows....
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Window Function Practice #30

Hard
4 views 24 Jan 2026
Table: Scores(user_id, score, created_at). Return each row with the rank of score within the same day....
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Join Practice #31

Easy
4 views 24 Jan 2026
Tables: A(id, val), B(id, val). Return ids present in both tables....
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Aggregation Practice #32

Medium
4 views 24 Jan 2026
Table: Sales(store_id, amount). Return store_id and average amount, only stores with at least 5 rows....
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Window Function Practice #33

Hard
11 views 24 Jan 2026
Table: Scores(user_id, score, created_at). Return each row with the rank of score within the same day....
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Join Practice #34

Easy
4 views 24 Jan 2026
Tables: A(id, val), B(id, val). Return ids present in both tables....
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Aggregation Practice #35

Medium
4 views 24 Jan 2026
Table: Sales(store_id, amount). Return store_id and average amount, only stores with at least 5 rows....
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Window Function Practice #36

Hard
4 views 24 Jan 2026
Table: Scores(user_id, score, created_at). Return each row with the rank of score within the same day....
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Join Practice #37

Easy
4 views 24 Jan 2026
Tables: A(id, val), B(id, val). Return ids present in both tables....
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Aggregation Practice #38

Medium
4 views 24 Jan 2026
Table: Sales(store_id, amount). Return store_id and average amount, only stores with at least 5 rows....
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Window Function Practice #39

Hard
5 views 24 Jan 2026
Table: Scores(user_id, score, created_at). Return each row with the rank of score within the same day....
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Join Practice #40

Easy
6 views 24 Jan 2026
Tables: A(id, val), B(id, val). Return ids present in both tables....
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TCP vs UDP (When to Use What)

Easy
8 views 24 Jan 2026
Explain the practical difference between TCP and UDP, and give one real use-case for each....
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What Happens in a TLS Handshake?

Medium
8 views 24 Jan 2026
Walk through a typical TLS handshake at a high level....
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Why NAT Exists

Easy
4 views 24 Jan 2026
What is NAT and why is it commonly used in home networks?...
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Three-Way Handshake #4

Easy
4 views 24 Jan 2026
Describe the TCP three-way handshake....
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Slow Start vs Congestion Avoidance #5

Medium
5 views 24 Jan 2026
In simple terms, what is TCP slow start?...
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Load Balancer Health Checks #6

Medium
5 views 24 Jan 2026
What is a health check and why do load balancers need it?...
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Idempotent HTTP Methods #7

Medium
8 views 24 Jan 2026
Which HTTP methods are idempotent and why does it matter?...
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CDN Edge Caching #8

Medium
6 views 24 Jan 2026
How does a CDN reduce latency?...
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WebSocket vs HTTP #9

Medium
4 views 24 Jan 2026
When would you choose WebSockets over plain HTTP?...
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Packet Loss Symptoms #10

Hard
5 views 24 Jan 2026
How does packet loss typically show up for users?...
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What is DNS Caching? #11

Easy
5 views 24 Jan 2026
Explain DNS caching and one common issue it can cause....
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HTTP Keep-Alive #12

Easy
7 views 24 Jan 2026
Why do HTTP connections often use keep-alive?...
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CIDR Basics #13

Easy
4 views 24 Jan 2026
What does /24 mean in CIDR notation?...
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Three-Way Handshake #14

Easy
5 views 24 Jan 2026
Describe the TCP three-way handshake....
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Slow Start vs Congestion Avoidance #15

Medium
5 views 24 Jan 2026
In simple terms, what is TCP slow start?...
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Load Balancer Health Checks #16

Medium
4 views 24 Jan 2026
What is a health check and why do load balancers need it?...
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Idempotent HTTP Methods #17

Medium
5 views 24 Jan 2026
Which HTTP methods are idempotent and why does it matter?...
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CDN Edge Caching #18

Medium
5 views 24 Jan 2026
How does a CDN reduce latency?...
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WebSocket vs HTTP #19

Medium
4 views 24 Jan 2026
When would you choose WebSockets over plain HTTP?...
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Packet Loss Symptoms #20

Hard
4 views 24 Jan 2026
How does packet loss typically show up for users?...
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What is DNS Caching? #21

Easy
6 views 24 Jan 2026
Explain DNS caching and one common issue it can cause....
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HTTP Keep-Alive #22

Easy
5 views 24 Jan 2026
Why do HTTP connections often use keep-alive?...
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CIDR Basics #23

Easy
5 views 24 Jan 2026
What does /24 mean in CIDR notation?...
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Three-Way Handshake #24

Easy
7 views 24 Jan 2026
Describe the TCP three-way handshake....
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Slow Start vs Congestion Avoidance #25

Medium
8 views 24 Jan 2026
In simple terms, what is TCP slow start?...
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Load Balancer Health Checks #26

Medium
6 views 24 Jan 2026
What is a health check and why do load balancers need it?...
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Idempotent HTTP Methods #27

Medium
5 views 24 Jan 2026
Which HTTP methods are idempotent and why does it matter?...
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CDN Edge Caching #28

Medium
6 views 24 Jan 2026
How does a CDN reduce latency?...
0 0 solutions View Details

WebSocket vs HTTP #29

Medium
4 views 24 Jan 2026
When would you choose WebSockets over plain HTTP?...
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Packet Loss Symptoms #30

Hard
5 views 24 Jan 2026
How does packet loss typically show up for users?...
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What is DNS Caching? #31

Easy
3 views 24 Jan 2026
Explain DNS caching and one common issue it can cause....
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HTTP Keep-Alive #32

Easy
8 views 24 Jan 2026
Why do HTTP connections often use keep-alive?...
0 0 solutions View Details

CIDR Basics #33

Easy
6 views 24 Jan 2026
What does /24 mean in CIDR notation?...
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Three-Way Handshake #34

Easy
2 views 24 Jan 2026
Describe the TCP three-way handshake....
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Slow Start vs Congestion Avoidance #35

Medium
6 views 24 Jan 2026
In simple terms, what is TCP slow start?...
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Load Balancer Health Checks #36

Medium
4 views 24 Jan 2026
What is a health check and why do load balancers need it?...
0 0 solutions View Details

Idempotent HTTP Methods #37

Medium
6 views 24 Jan 2026
Which HTTP methods are idempotent and why does it matter?...
0 0 solutions View Details

CDN Edge Caching #38

Medium
3 views 24 Jan 2026
How does a CDN reduce latency?...
0 0 solutions View Details

WebSocket vs HTTP #39

Medium
4 views 24 Jan 2026
When would you choose WebSockets over plain HTTP?...
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Packet Loss Symptoms #40

Hard
4 views 24 Jan 2026
How does packet loss typically show up for users?...
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Design URL Shortener

Medium
4 views 24 Jan 2026
Design a URL shortener like bit.ly. Focus on APIs, storage, and scaling....
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Design Rate Limiter

Medium
4 views 24 Jan 2026
Design a rate limiter for an API gateway....
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Design Chat App #3

Hard
4 views 24 Jan 2026
1:1 chat with typing indicator and read receipts....
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Design Feed (Timeline) #4

Hard
5 views 24 Jan 2026
Home feed like Twitter: rank posts and serve fast....
0 0 solutions View Details

Design File Storage #5

Hard
3 views 24 Jan 2026
Upload, download, and share large files....
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Design Notification System #6

Medium
5 views 24 Jan 2026
Push notifications for mobile/web. What are the main components?...
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Design Logging Pipeline #7

Medium
3 views 24 Jan 2026
Centralize logs from many services and make them searchable....
0 0 solutions View Details

Design Chat App #8

Hard
3 views 24 Jan 2026
1:1 chat with typing indicator and read receipts....
0 0 solutions View Details

Design Feed (Timeline) #9

Hard
3 views 24 Jan 2026
Home feed like Twitter: rank posts and serve fast....
0 0 solutions View Details

Design File Storage #10

Hard
4 views 24 Jan 2026
Upload, download, and share large files....
0 0 solutions View Details

Design Notification System #11

Medium
5 views 24 Jan 2026
Push notifications for mobile/web. What are the main components?...
0 0 solutions View Details

Design Logging Pipeline #12

Medium
5 views 24 Jan 2026
Centralize logs from many services and make them searchable....
0 0 solutions View Details

Design Chat App #13

Hard
4 views 24 Jan 2026
1:1 chat with typing indicator and read receipts....
0 0 solutions View Details

Design Feed (Timeline) #14

Hard
6 views 24 Jan 2026
Home feed like Twitter: rank posts and serve fast....
0 0 solutions View Details

Design File Storage #15

Hard
5 views 24 Jan 2026
Upload, download, and share large files....
0 0 solutions View Details

Design Notification System #16

Medium
5 views 24 Jan 2026
Push notifications for mobile/web. What are the main components?...
0 0 solutions View Details

Design Logging Pipeline #17

Medium
4 views 24 Jan 2026
Centralize logs from many services and make them searchable....
0 0 solutions View Details

Design Chat App #18

Hard
5 views 24 Jan 2026
1:1 chat with typing indicator and read receipts....
0 0 solutions View Details

Design Feed (Timeline) #19

Hard
5 views 24 Jan 2026
Home feed like Twitter: rank posts and serve fast....
0 0 solutions View Details

Design File Storage #20

Hard
5 views 24 Jan 2026
Upload, download, and share large files....
0 0 solutions View Details

Design Notification System #21

Medium
6 views 24 Jan 2026
Push notifications for mobile/web. What are the main components?...
0 0 solutions View Details

Design Logging Pipeline #22

Medium
3 views 24 Jan 2026
Centralize logs from many services and make them searchable....
0 0 solutions View Details

Design Chat App #23

Hard
3 views 24 Jan 2026
1:1 chat with typing indicator and read receipts....
0 0 solutions View Details

Design Feed (Timeline) #24

Hard
3 views 24 Jan 2026
Home feed like Twitter: rank posts and serve fast....
0 0 solutions View Details

Design File Storage #25

Hard
4 views 24 Jan 2026
Upload, download, and share large files....
0 0 solutions View Details

Design Notification System #26

Medium
4 views 24 Jan 2026
Push notifications for mobile/web. What are the main components?...
0 0 solutions View Details

Design Logging Pipeline #27

Medium
4 views 24 Jan 2026
Centralize logs from many services and make them searchable....
0 0 solutions View Details

Design Chat App #28

Hard
4 views 24 Jan 2026
1:1 chat with typing indicator and read receipts....
0 0 solutions View Details

Design Feed (Timeline) #29

Hard
4 views 24 Jan 2026
Home feed like Twitter: rank posts and serve fast....
0 0 solutions View Details

Design File Storage #30

Hard
4 views 24 Jan 2026
Upload, download, and share large files....
0 0 solutions View Details

Design Notification System #31

Medium
5 views 24 Jan 2026
Push notifications for mobile/web. What are the main components?...
0 0 solutions View Details

Design Logging Pipeline #32

Medium
3 views 24 Jan 2026
Centralize logs from many services and make them searchable....
0 0 solutions View Details

Design Chat App #33

Hard
3 views 24 Jan 2026
1:1 chat with typing indicator and read receipts....
0 0 solutions View Details

Design Feed (Timeline) #34

Hard
4 views 24 Jan 2026
Home feed like Twitter: rank posts and serve fast....
0 0 solutions View Details

Design File Storage #35

Hard
4 views 24 Jan 2026
Upload, download, and share large files....
0 0 solutions View Details

Design Notification System #36

Medium
3 views 24 Jan 2026
Push notifications for mobile/web. What are the main components?...
0 0 solutions View Details

Design Logging Pipeline #37

Medium
5 views 24 Jan 2026
Centralize logs from many services and make them searchable....
0 0 solutions View Details

Design Chat App #38

Hard
3 views 24 Jan 2026
1:1 chat with typing indicator and read receipts....
0 0 solutions View Details

Design Feed (Timeline) #39

Hard
4 views 24 Jan 2026
Home feed like Twitter: rank posts and serve fast....
0 0 solutions View Details

Design File Storage #40

Hard
3 views 24 Jan 2026
Upload, download, and share large files....
0 0 solutions View Details

Shortest Path BFS

Hard
6 views 24 Jan 2026
Input provides {x}. Implement bfs to output shortest distance (edges count) or -1....
0 0 solutions View Details

Graph Shortest Path Class

Hard
5 views 24 Jan 2026
Input provides {x}. Create Graph class with bfs(s,t) method. Output shortest distance or -1....
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Sort Mixed Tokens

Hard
6 views 24 Jan 2026
You get {x}. Token types: INT, FLOAT (with dot), WORD. Sort by type order INT then FLOAT then WORD. For ints sort by numeric value, for floats sort by numeric value, for words sort lexicographically. ...
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Trie Prefix Counter

Hard
6 views 24 Jan 2026
We have {x}. Create Trie class. For COUNT output how many added words have this prefix....
0 0 solutions View Details

Dijkstra Shortest Path (Many Cases)

Hard
6 views 24 Jan 2026
For each testcase you get weighted undirected graph. Output shortest distance from 1 to n. If unreachable output -1....
0 0 solutions View Details

Median Finder Class

Hard
5 views 24 Jan 2026
You will receive q commands: ADD x or MEDIAN. Create MedianFinder class using two heaps. For MEDIAN output lower median (floor for even count)....
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Distinct In Every Window

Hard
4 views 24 Jan 2026
For each testcase you get n, k and n integers. For each window of size k output how many distinct numbers are inside....
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First Repeat Prefix Sum

Hard
6 views 24 Jan 2026
We have {x}. If never repeats, output -1....
0 0 solutions View Details

Merge Intervals

Hard
5 views 24 Jan 2026
Input provides {x}. Write function merge(intervals) and output merged intervals sorted....
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Segment Tree Range Sum

Hard
5 views 24 Jan 2026
Given {x}, Two types: 1 i x means set a[i]=x, 2 l r means output sum of a[l..r] (1-based). Implement build/update/query helpers....
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Sliding Window Maximum

Hard
5 views 24 Jan 2026
You're given {x}. For each window output maximum. Use a deque....
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Smallest Subarray Sum at Least S

Hard
5 views 24 Jan 2026
You get {x}. Compute the minimum length of a contiguous subarray with sum >= S. If not found, output 0....
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Tree Diameter For Each Testcase

Hard
6 views 24 Jan 2026
For each testcase you get a tree with n nodes. Output the diameter length (number of edges on longest path)....
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Binary Search Function

Medium
6 views 24 Jan 2026
Consider {x}. Output result....
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Longest Common Prefix

Medium
6 views 24 Jan 2026
Given {x}, Output their longest common prefix. If no common prefix, output EMPTY....
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Longest Increasing Prefix Length

Medium
5 views 24 Jan 2026
For each testcase you get n numbers. Compute length of the longest prefix that is strictly increasing....
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Sliding Window Maximum (Algorithms)

Medium
6 views 24 Jan 2026
For each testcase you get n, k and n numbers. Output max of each window of size k (space-separated)....
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Sort By Frequency

Medium
7 views 24 Jan 2026
For each testcase you get n integers. Sort them by frequency descending. If frequency same, smaller number first. Output sorted list....
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All Subset Sums

Hard
18 views 24 Jan 2026
Consider {x}. Use recursion function dfs(i,cur) to generate all subset sums. Output sums sorted....
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Fast Power Mod Function

Hard
6 views 24 Jan 2026
We have {x}....
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Kth Switch Toggle

Hard
4 views 24 Jan 2026
You have n bulbs all OFF. For i from 1 to n, toggle every i-th bulb. At the end, how many bulbs are ON? Output count....
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Longest Subarray with At Most K Distinct

Hard
5 views 24 Jan 2026
Input provides {x}. Compute length of the longest contiguous subarray that has at most K distinct numbers....
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Maximum Subarray Sum Circular

Hard
7 views 24 Jan 2026
You're given {x}. Compute maximum subarray sum in circular array and output it....
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Prefix Sums Print

Easy
5 views 24 Jan 2026
Given {x}, Output prefix sum after each element (same order)....
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Segment Tree Range Minimum

Hard
7 views 24 Jan 2026
Consider {x}. Build SegmentTree class with update(i,x) and query(l,r) returning minimum. Output query answers....
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String Hash Queries

Hard
6 views 24 Jan 2026
Input provides {x}. Implement to build prefix hashes and answer hash values mod 1000000007....
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Sum Numbers With Prefix Base

Hard
5 views 24 Jan 2026
We have {x}. Each token can be decimal like 15, binary like 0b1010, octal like 0o12, or hex like 0xFF. Tokens can also have a leading '-' sign. Convert all to integer and output the sum....
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Topological Order Or Cycle

Hard
6 views 24 Jan 2026
For each testcase you get a directed graph. If topological order exists, output one order. If cycle exists, output CYCLE....
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Binary XOR

Medium
4 views 24 Jan 2026
Two binary strings a and b are provided (same length). Compute bitwise XOR and output result without leading zeros (output 0 if all zero)....
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Count Set Bits

Medium
5 views 24 Jan 2026
One non-negative integer n is provided. Count how many 1 bits are in binary representation and output it....
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Integer to Binary with Variables

Medium
6 views 24 Jan 2026
You get {x}. Output its binary without using bin(). Use repeated division and variables....
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Kth Bit Check

Medium
6 views 24 Jan 2026
You're given {x}. Output 1 if k-th bit (0-based) of n is set, else 0....
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Kth Largest Element

Medium
6 views 24 Jan 2026
For each testcase you get n, k and n integers. Output the k-th largest element....
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Kth Smallest Quickselect

Medium
6 views 24 Jan 2026
You're given {x}. Compute kth smallest element using quickselect style and output it....
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Prefix Count Queries

Medium
6 views 24 Jan 2026
Consider {x}. For each word, count all its prefixes. Then q prefixes are provided. For each prefix output how many words start with it....
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Prefix Sum Function

Medium
4 views 24 Jan 2026
Consider {x}. Write function build_prefix(arr) and answer sums fast....
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Sort By Frequency (Algorithms)

Medium
5 views 24 Jan 2026
We have {x}. Sort them by frequency ascending, if tie by value ascending. Output sorted list....
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Sort Circles By Area

Medium
6 views 24 Jan 2026
Consider {x}. Create Circle class with area() and sort circles by area ascending. Output sorted radii....
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Subarray Sum Positive

Medium
6 views 24 Jan 2026
Consider {x}. Output YES if there exists a subarray with sum exactly S else NO....
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Add Without Plus

Hard
4 views 24 Jan 2026
Consider {x}. Add them without using + or -. Use bit operations and output sum....
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Rotate String by K

Medium
6 views 24 Jan 2026
A string s and integer k are provided. Rotate string to the right by k positions and output....
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Rotate String Right

Medium
5 views 24 Jan 2026
For each testcase you get string s and integer k. Rotate string to the right by k and output the new string....
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Boolean XOR Expression

Hard
6 views 24 Jan 2026
A boolean string s of 0/1 and a boolean string t of 0/1 are provided, same length. Treat them as bits and compute (s XOR t) as a new string. Output it....
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Decode Nested Repeat

Hard
6 views 24 Jan 2026
A string is provided in form like 3[a2[c]] where number means repeat. Decode and output the final string....
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Normalize Number String

Hard
6 views 24 Jan 2026
A number is provided as string. It may have + sign, leading zeros, and decimal part. Normalize it: remove +, remove extra leading zeros, remove trailing zeros in decimal, and if it becomes -0 or 0.0 t...
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Remove Pattern Repeatedly

Hard
7 views 24 Jan 2026
Input provides {x}. Remove every occurrence of p from s while scanning left to right (like stack remove). Output final string....
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Reverse String

Easy
6 views 24 Jan 2026
Input is a single string s is provided (no trailing spaces needed). Output the reversed string....
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Rolling Hash Variable

Hard
4 views 24 Jan 2026
You're given {x}. Compute rolling hash: h=0; for each char c: h=(h*B+ord(c))%M. Output h....
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Split Array Largest Sum

Hard
6 views 24 Jan 2026
You're given {x}. Split array into m non-empty continuous parts to minimize the maximum part sum. Output that minimum possible value....
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String Length Info

Easy
5 views 24 Jan 2026
Input is a single string s is provided (can contain spaces). Output its length, first character and last character. If string is empty, output 0 - -....
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Unescape Simple String

Hard
5 views 24 Jan 2026
A quoted string is provided. It can contain escapes: \\\\n, \\\\t, \\\\\\\\, and \\\\\. Unescape it and output two integers: length and checksum (sum of char codes modulo 256)."....
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Wildcard Match

Hard
6 views 24 Jan 2026
You get {x}. Output YES if pattern matches whole string else NO....
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Check Array Sorted For Each Case

Medium
4 views 24 Jan 2026
Consider {x}. Each testcase has n and array. Output YES if array is non-decreasing else NO....
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Remove Adjacent Duplicates

Medium
7 views 24 Jan 2026
For each testcase you get string s. Repeatedly remove adjacent equal characters using a stack idea. Output final string (or EMPTY)....
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Remove All Digits

Medium
6 views 24 Jan 2026
A string s is provided. Remove all digits (0-9) and output remaining string....
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Reverse Map Count

Medium
6 views 24 Jan 2026
You're given {x}. Build reverse mapping: for each value, how many keys map to it. Output values sorted with their counts....
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Rotate List Right

Medium
5 views 24 Jan 2026
Input provides {x}. Rotate list to the right by k positions and output....
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Run Length Decode

Medium
6 views 24 Jan 2026
An encoded string is provided like a3b2c (letters with optional number). Decode and output the original string....
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Run Length Encode

Medium
6 views 24 Jan 2026
A string s is provided. Compress it using run-length encoding as: char followed by count (only when count>1). Output encoded string....
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String to Integer Parser

Medium
5 views 24 Jan 2026
A string s is provided (maybe with leading spaces and sign). Parse first integer like simple atoi. If no number, output 0....
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Connectivity Queries (DSU)

Hard
4 views 24 Jan 2026
Consider {x}. Make DSU class with find and union. Queries: UNION u v, ASK u v. For ASK output YES if connected else NO....
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Deque Commands With Errors

Hard
5 views 24 Jan 2026
You will receive q commands: PUSHFRONT x, PUSHBACK x, POPFRONT, POPBACK. Start empty. On POP when empty, output ERROR and stop. Else after all commands output final deque as space-separated or EMPTY....
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Detect Uninitialized Read

Hard
7 views 24 Jan 2026
You will receive n statements in a tiny language: 'set x v' or 'add x y' meaning x = x + y. If add uses a variable that was never set before (for x or y), count it as a bad read. Output badReadCount....
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Find First Unset Variable

Hard
6 views 24 Jan 2026
You will receive q queries like GET name or SET name value. Maintain variables in a dict. For each GET, output value if present else UNSET....
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Huge Power Mod (Exponent as String)

Hard
6 views 24 Jan 2026
Integers a and m are provided, and exponent b is provided as a very large decimal string. Output (a^b) % m....
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JSON Type Counter

Hard
7 views 24 Jan 2026
A JSON array is provided in one line, like [1,2,true,null]. Count how many numbers, strings, booleans, and null values. Output counts in order: num str bool null....
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Longest Palindromic Substring Length

Hard
6 views 24 Jan 2026
A string s is provided (no spaces). Compute length of longest palindromic substring. Use linear-time method....
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Merge Two Score Lists

Easy
5 views 24 Jan 2026
We have {x}. Make final score for each key as sum of scores from both lists (missing is 0). Output keys sorted with their final score....
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Minimum Insertions Palindrome

Hard
7 views 24 Jan 2026
A string s is provided (no spaces). Compute minimum insertions needed to make it a palindrome. Output the number....
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Nested Dictionary Path

Hard
5 views 24 Jan 2026
You will receive q commands on a nested dictionary: SET path value, GET path. Path is dot separated like a.b.c. For GET output value if exists else NOT FOUND....
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Pack Bytes to Hex

Hard
6 views 24 Jan 2026
Given {x}, .255). Put them into a bytes object and output hex string in uppercase....
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Range Add Queries (Difference Array)

Hard
8 views 24 Jan 2026
For each testcase you get n and q updates. Each update adds val to all positions l..r (1-based). After all updates output final array....
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Remove Spaces

Easy
6 views 24 Jan 2026
A string s is provided. Remove all space characters and output the new string....
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Run-Length Compression

Hard
7 views 24 Jan 2026
Input provides {x}. Example aaabb becomes a3b2. Output compressed string....
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Smallest Rotation

Hard
10 views 24 Jan 2026
A string s is provided. Consider all rotations of s. Output the lexicographically smallest rotation....
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Smallest Subsequence of Length K

Hard
7 views 24 Jan 2026
A string s and integer k are provided. Pick a subsequence of length k (keep order) with smallest lexicographic value. Output that subsequence....
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Smallest Window Contains Pattern

Hard
6 views 24 Jan 2026
You get {x}. Compute the length of smallest substring of s that contains all characters of p with at least same counts. If not possible output 0....
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Stack Operations

Easy
6 views 24 Jan 2026
Input provides {x}. Start empty list. POP on empty does nothing. At end output size and last element (or EMPTY)....
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String Number Add

Easy
5 views 24 Jan 2026
A number is provided as a string x and an integer y is provided. Convert x to int and output x+y....
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Swap Values of Two Keys

Easy
5 views 24 Jan 2026
You're given {x}. Then two keys k1 and k2 are provided. If both keys exist, swap their values. Finally output value of k1 and value of k2 (use NA if a key does not exist)....
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Person Greeting

Easy
9 views 24 Jan 2026
Name and age are provided. Create class Person with method greet() that returns 'Hi , you are '. Output greet()....
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Rectangle Area

Easy
8 views 24 Jan 2026
Length and width are provided. Create Rectangle class with area() method. Output area as integer....
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