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The journey of every round

Every round-trip in the corpus is public. Open one to see the prompt, the zero-point index, the baseline response, the enhanced response, and how each grader read the difference. Leave a comment if a grader's reading lands — or doesn't.

FilterVerdictallBetterSameWorseDomainallcsharppythonhr-lawhousing-lawmath428 rounds
#84511 May 26

Create an ApiController class with a single GET ActionResult that returns a product or NotFound when no product matches the route id.

V1BetterV2—ΔL+0.0csharp
#84411 May 26

Write an IMiddleware implementation that adds an X-Request-ID header to every response. Show it being registered in the request pipeline.

V1BetterV2—ΔL+0.5csharp
#84310 May 26

Write a custom equality comparer (IEqualityComparer<Person>) that treats two Person records as equal when Email lowercased matches. Include GetHashCode.

V1BetterV2—ΔL—csharp
#84210 May 26

Write a Regex that matches IPv4 addresses in the form '1.2.3.4' (each octet 0–255). Use Regex.Match on a sample string.

V1WorseV2—ΔL—csharp
#84110 May 26

Write a ReadOnlySpan<byte>-based UTF-8 BOM check: return true if the span starts with the bytes 0xEF 0xBB 0xBF.

V1WorseV2—ΔL—csharp
#84010 May 26

Write a using-block over a StreamReader that reads each line and counts occurrences of the word 'foo'. No async.

V1BetterV2—ΔL—csharp
#83910 May 26

Write a generic Swap<T> method that swaps two ref T parameters. Include an example call with two ints.

V1SameV2—ΔL—csharp
#83810 May 26

Implement a multitenant request-scoped ITenantInfo resolver that reads the tenant id from a custom header and falls back to subdomain.

V1BetterV2—ΔL-0.3csharp
#83710 May 26

Build a SignalR Hub that lets clients subscribe to a 'price-tick' channel and broadcasts ticks to all subscribers on a one-second timer.

V1WorseV2—ΔL+0.0csharp
#83610 May 26

Implement a generic repository for read-only access to entities by id using a DbContext. Include AsNoTracking and a CancellationToken parameter.

V1BetterV2—ΔL+0.0csharp
#83510 May 26

Write a BackgroundService that reads work items from an in-memory queue and processes each one with a small delay, with graceful shutdown handling.

V1BetterV2—ΔL+0.0csharp
#83410 May 26

Write an IMiddleware implementation that adds an X-Request-ID header to every response. Show it being registered in the request pipeline.

V1BetterV2—ΔL+0.5csharp
#80810 May 26

Find the date with the highest number of new signups in a users table.

V1BetterV2—ΔL—csharp
#80710 May 26

Use HAVING to filter aggregate results: orders with more than 5 line items.

V1BetterV2—ΔL—csharp
#80610 May 26

Write a SQL query joining 4 tables (customers, orders, line_items, products) to produce a customer-order-product report.

V1BetterV2—ΔL—csharp
#80510 May 26

Find products in the top 10 percent by revenue using NTILE.

V1BetterV2—ΔL—csharp
#80410 May 26

Calculate the gap in days between consecutive logins per user using LAG.

V1BetterV2—ΔL—csharp
#80310 May 26

Use EXISTS to find customers with at least one cancelled order.

V1BetterV2—ΔL—csharp
#80210 May 26

Find the median salary in each department using window functions.

V1BetterV2—ΔL—csharp
#80110 May 26

Write a recursive CTE to walk an employee-manager hierarchy from any starting employee.

V1BetterV2—ΔL—csharp
#80010 May 26

Use UNION to combine current_employees and former_employees, marking source.

V1BetterV2—ΔL—csharp
#79910 May 26

Find orders where the order_date is later than the ship_date.

V1BetterV2—ΔL—csharp
#79810 May 26

Write a SQL query that returns products and their cumulative sales over time.

V1BetterV2—ΔL—csharp
#79710 May 26

Calculate a moving 7-day average of daily_sales using a window function.

V1BetterV2—ΔL—csharp