SquadStack.ai OA (On - Campus, Core Engineer)

SquadStack.ai OA Experience

• 10 Aptitude questions
• 15 Core CS questions
• 2 coding questions
• 1 SQL question

Had negative marking (-0.5)

The two coding questions were:

1. Decode Ways - Leetcode 91 (with a twist)

LeetCode 91 - Decode Ways was the base question. It had a small twist that the way you read a character is associated with a cost and you have to minimise the cost of reading the string. Solvable if you had solved this before.

2. Minimum Seats Required - Car Pooling — LeetCode 1094

You are given a car that travels in one direction along a route.

You are given an array stops, where each element is:

[p, f, t]

p = number of passengers f = point where the passengers get into the car t = point where the passengers get out of the car

Passengers can get in and out at different points along the route.

At each point, passengers who are getting down leave the car first, and then new passengers are picked up.

Find the minimum number of seats required in the car to accommodate all passengers.

LeetCode 1094 — Car Pooling

SQL Problem: Find the Dominant Seller

Problem Description

You are given two tables: Sellers and Orders.

Sellers

Column	Type	Description
seller_id	INT	Primary key
seller_name	VARCHAR	Name of the seller

Orders

Column	Type	Description
order_id	INT	Primary key
seller_id	INT	Foreign key referencing Sellers
item_qty	INT	Quantity of items sold
item_rate	DECIMAL	Rate per item

Task

Calculate the total revenue generated by each seller:

total_revenue = SUM(item_qty * item_rate)

A seller is considered a Dominant Seller if their total revenue is strictly greater than the combined total revenue of all other sellers.

Return the seller_id and total_revenue of all dominant sellers.

Example

Suppose the total revenues are:

Seller 1 → 1000
Seller 2 → 300
Seller 3 → 200

Seller 1 is dominant because:

1000 > 300 + 200

Therefore, the answer is:

seller_id | total_revenue
----------|--------------
1         | 1000

---

SQL Solution

WITH seller_revenue AS (
    SELECT
        seller_id,
        SUM(item_qty * item_rate) AS total_revenue
    FROM Orders
    GROUP BY seller_id
),
total_revenue AS (
    SELECT SUM(total_revenue) AS overall_revenue
    FROM seller_revenue
)
SELECT
    sr.seller_id,
    sr.total_revenue
FROM seller_revenue sr
CROSS JOIN total_revenue tr
WHERE sr.total_revenue > tr.overall_revenue - sr.total_revenue;

Explanation

Let:

R = seller's revenue
T = total revenue of all sellers

Revenue generated by all other sellers is:

T - R

So the condition for a dominant seller is:

R > T - R

which is equivalent to:

2R > T

The CTE first calculates revenue per seller, then calculates the overall revenue, and finally identifies sellers whose revenue is greater than the combined revenue of everyone else.