How do I practice coding and algorithm questions?

Use PracHub's coding console to write, test, and debug your solutions in Python or JavaScript. View hints, test against sample inputs, and compare with official solutions.

What difficulty level is this coding question?

This is a hard difficulty Coding & Algorithms question, commonly asked during Technical Screen rounds at Squarepoint.

What role is this question designed for?

This question is commonly asked for Data Scientist candidates at Squarepoint during technical interviews.

Maximize profit from one or many stock trades

Quick Overview

This question evaluates algorithmic problem-solving skills, particularly efficient array processing and profit-optimization across single-transaction and multiple-transaction variants, along with time and space complexity analysis.

Maximize profit from one or many stock trades

Company: Squarepoint

Role: Data Scientist

Category: Coding & Algorithms

Difficulty: hard

Interview Round: Technical Screen

You are given an integer array `prices` where `prices[i]` is the price of a stock on day `i` (0-indexed). Answer the following two subproblems: 1. **Single transaction** - You may complete at most **one** transaction: choose one day to buy and a later day to sell (must buy before you sell). - You are not allowed to short-sell. - Return the **maximum profit** you can achieve. If you cannot make any profit, return `0`. 2. **Multiple transactions** - You may complete **as many transactions as you like** (i.e., buy and sell multiple times), but you **cannot hold more than one share at a time** (you must sell the stock before you buy again). - You are not allowed to short-sell. - Return the **maximum total profit** you can achieve. Assume: - `1 <= n <= 10^5`, where `n` is the length of `prices`. - `0 <= prices[i] <= 10^4`. Design efficient algorithms for both subproblems and analyze their time and space complexity.

Quick Answer: This question evaluates algorithmic problem-solving skills, particularly efficient array processing and profit-optimization across single-transaction and multiple-transaction variants, along with time and space complexity analysis.

Max Profit from One Stock Transaction

Return maximum profit from at most one buy before one sell.

Constraints

Inputs are Python literals matching the function signature.
Return a deterministic exact-match value.

Examples

Input: ([7,1,5,3,6,4],)

Expected Output: 5

Explanation: Buy low sell high.

Input: ([7,6,4,3,1],)

Expected Output: 0

Explanation: No profit.

Input: ([1],)

Expected Output: 0

Explanation: Single price.

Hints

Choose a representation that makes the requested operation direct.
Handle empty inputs and boundary cases first.

Max Profit from Many Stock Transactions

Return maximum total profit from any number of non-overlapping buy/sell transactions.

Constraints

Inputs are Python literals matching the function signature.
Return a deterministic exact-match value.

Examples

Input: ([7,1,5,3,6,4],)

Expected Output: 7

Explanation: Take every positive rise.

Input: ([1,2,3,4,5],)

Expected Output: 4

Explanation: Monotone increasing.

Input: ([7,6,4,3,1],)

Expected Output: 0

Explanation: No profit.

Hints

Choose a representation that makes the requested operation direct.
Handle empty inputs and boundary cases first.

Last updated: Jun 27, 2026

Loading coding console...