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Quick facts

• Difficulty: MEDIUM
• Problem: Coin Change II
• Main tags: Array, Dynamic Programming

What the problem is really asking

The input gives a target amount and a list of coin denominations. Each denomination can be used as many times as needed.

The task is to count how many distinct combinations can make the amount exactly. It is not asking for the minimum number of coins, and it is not asking whether the amount is possible at all.

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Dark matter as a hidden ecosystem

This article argues that dark matter may be far more elaborate than the usual picture of one missing particle waiting to be caught in a detector. Kathryn Zurek describes a growing alternative: dark matter could belong to an entire “dark sector” with its own particles, forces and internal dynamics. In that view, the visible universe is not simply missing one ingredient. It may be sharing reality with a second, largely inaccessible layer of physics that almost never interacts with ordinary matter except through gravity.

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Selected problem: Video Streaming Platform

Scope: Design a global video-on-demand platform that supports resumable creator uploads, transcoding, metadata/search, and adaptive-bitrate playback on web, mobile, and TV clients; exclude recommendations, ads, and live streaming from the first version.

Problem framing

This is the classic “design YouTube / Netflix-style VOD platform” interview. Grokking is useful for the interview flow: clarify scope, define APIs early, size uploads versus reads, and separate large media blobs from metadata. Alex Xu adds the practical serving path: object storage for source and encoded media, an asynchronous transcoding pipeline, CDN-based delivery, and a metadata control plane. DDIA sharpens the deeper answer: treat search indexes, counters, and playback-ready state as derived data maintained from durable logs and background workflows, not as one giant transactional database.

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What this article is about

This summary covers The Economist’s April 11th, 2026 Leaders article listed in the contents as Artemis II and published under the headline The inspiration of Artemis II.

The article’s argument is that Artemis II matters not because it is producing startling new science, but because it restores a human perspective that has been missing from spaceflight for decades. The mission’s real achievement is emotional and political: it reminds people on Earth what it means to have human beings out there, seeing the Moon and the Earth directly rather than through archives or robotic instruments. But the article also warns that this renewed wonder will not last on its own. A lunar programme that hopes to endure will eventually need more than a reprise of Apollo-era feeling.

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A short flight that explains the whole sport

Richard Dery’s essay starts with an apparently absurd ratio: hours of driving, setup, waiting, and wind-watching for just fifteen minutes in the air above Ellenville, New York. On paper, the trade looks ridiculous. Yet the article argues that this imbalance is exactly what makes flying meaningful. The scarcity sharpens the experience, and the long prelude only heightens the intensity of the brief window when everything finally lines up.

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MrBeast employee alleges she was harassed for years and fired after maternity leave in a new lawsuit (r/news)

• EkorrenHJ: I had no opinion on MrBeast until I saw him om a podcast where he kept talking about how much he despised “mediocre people.” That made me recognize he probably fostered toxic working conditions.

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Do NOT join Microsoft Right Now - Mass cuts inbound…! (Blind)

• yepyepyep1 (Microsoft): That wasn’t Amy Hood

• EditConfig (Google): Don’t worry, VPs and c-suite are not subject to review or layoffs, and will get millions in bonuses and refreshers for reduce operating expenses.

Is Meta spying on me? (Blind)

• San-Ti 👾 (Baxter): Bro, Meta’s business model is spying on everyone. You guy’s build spying tool, tracking everyone even those not signed up for meta products.

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A ski trip framed as apprenticeship instead of conquest

Chris Christie’s “Rhythm in Place” is stronger than a standard destination feature because it states its thesis almost immediately: far north on Greenland’s east coast, safe backcountry travel is informed by the methods of local hunters. The opening pages make East Greenland feel genuinely alien to a ski mountaineer used to more familiar ranges. The plane drops through clouds over the Denmark Strait, the pack ice below looks like a moonscape, and the landscape is described as so wild and remote that it demands something beyond conventional ski-mountaineering skill. That sets up the article’s real subject, which is not just skiing in an exotic place, but learning how to move through it without pretending prior experience automatically translates.

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Quick facts

• Difficulty: MEDIUM
• Problem: Coin Change
• Main tags: Array, Dynamic Programming, Breadth-First Search

What the problem is really asking

The input gives a set of coin denominations and a target amount. Each coin can be used as many times as needed.

The goal is not to count how many different ways the amount can be formed. The goal is to find the fewest coins needed to reach the exact amount. If the amount cannot be formed exactly, the answer is -1.

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What this article is really about

Richard Panek uses cosmology as a case study in scientific humility. The article’s main claim is that astronomy repeatedly treats some picture of the universe as obviously true, only to discover later that the “obvious” picture was built on hidden assumptions.