Scenarios/Solving workspace

Pair Sum

Practice — repeatable, unscored

Read first — you never hand-write code here.

Your agent writes solution.* on its own computer. The workspace file panel is a read-only, revisioned view: every agent turn flushes the newest revision there. You direct, review, and test — the agent types.

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Stage 1 of 3 · Core pairEasy · 20 min · 4 prompts

Sample preview. Each attempt gets its own brief and example values. Your exact requirements appear when you start an attempt.

Find two numbers that add to a target and return their positions. Walk the list once, remembering each number seen: for two_sum([2, 7, 11, 15], 9), 9 - 2 = 7 is already seen, so the answer is [0, 1].

Core pair

Write two_sum(nums, target), which returns the indices of the two numbers that add up to target. Constraints: exactly one solution exists, and the same element cannot be used twice. Aim for a single pass.

Sample example

Input: two_sum([2,7,11,15], 9)
Expected output: [0, 1]

Starter file · Python

Preview

def two_sum(nums, target):
    # your code here
    pass

All three stages

Stage 1 · Core pair (previewed above)
Core sample — implement the base behavior against one visible example.
Stage 2 · locked until stage 1 passes
Edges and extensions — adapt the same solution; every visible example is shown.
Stage 3 · locked until stage 2 passes
Hidden acceptance — final coverage; finishing runs the full suite including hidden tests.

Each attempt gets its own brief and example values. Exact stage 2–3 requirements appear in the workspace as you unlock them.

Your agent

Ready to start

Solution languageOnline computerProviderModel — pick a providerConnect a computer and pick a provider to see its models.

Checking your paired computers…

Models come from your installed agent. Local provider usage and billing apply.

Solving with: no computer selected · no provider selected · agent default model. Change these above before starting.

Ready for your attempt?

Open your workspace with its own question variant, agent chat, and solution file. Write your first prompt there when you are ready.

Starting sets up the workspace. Your agent begins solving only after you send a prompt on the attempt page.

1. Read the question and choose your agent and model.
2. Start an attempt to open your dedicated workspace.
3. Prompt your agent there, review its code, and run checks.
4. Unlock stages 2–3, then finish for code acceptance.

All attempt history · rename, archive, or restore

Your attempts

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History belongs to this browser session. Reconnecting a computer does not delete it. Archive retains the attempt and its trace. Delete hides it in this browser only.

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