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Quick facts

• Difficulty: MEDIUM
• Problem: Next Permutation
• Main tags: Array, Two Pointers

What the problem is really asking

The array represents one permutation of the numbers.

The task is to mutate it into the very next permutation in lexicographic order, which means:

• make the number just a little larger
• keep that increase as small as possible
• do everything in place

If the current permutation is already the largest possible one, such as [3, 2, 1], then there is no larger answer. In that case, the correct result is the smallest permutation, which is ascending order.

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Quick facts

• Difficulty: MEDIUM
• Problem: Decode String
• Main tags: String, Stack, Recursion

What the problem is really asking

The input is an encoded string where patterns like 3[ab] mean “repeat ab three times.” The tricky part is that the repeated part can itself contain more encoded pieces, such as 3[a2[c]].

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Quick facts

• Difficulty: MEDIUM
• Problem: Maximum Subarray
• Main tags: Array, Divide and Conquer, Dynamic Programming

What the problem is really asking

The input is an integer array, and the task is to choose one contiguous subarray whose sum is as large as possible.

The important constraint is contiguity. This is not “pick the best numbers anywhere in the array.” Once a starting point is chosen, the subarray must be one uninterrupted block.

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Quick facts

• Difficulty: MEDIUM
• Problem: Merge Intervals
• Main tags: Array, Sorting

What the problem is really asking

The input is a list of inclusive intervals like [start, end]. The goal is to combine every set of overlapping intervals and return the smallest list of non-overlapping intervals that covers the same ranges.

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Quick facts

• Difficulty: MEDIUM
• Problem: Reverse Integer
• Main tags: Math

What the problem is really asking

Given a signed 32-bit integer, reverse its decimal digits.

Examples:

• 123 becomes 321
• -123 becomes -321
• 120 becomes 21

The catch is that the answer must still fit inside the signed 32-bit range:

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A mission that is halfway to its real goal

Jonathan O’Callaghan’s article is not mainly about the Perseverance rover itself. It is about the awkward possibility that NASA may complete the expensive, glamorous first half of a historic Mars experiment and then abandon the second half before the science can pay off.

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What happened

Techmeme surfaced this story in its April 11, 2026 roundup, and the original report is Uncovering Webloc: An Analysis of Penlink’s Ad-based Geolocation Surveillance Tech.

Citizen Lab’s report describes Webloc as a commercial surveillance system built from ordinary advertising and app exhaust rather than a classic zero-click exploit or telecom intercept. The researchers say the platform, developed by Cobwebs Technologies and now sold by Penlink, gives customers access to a constantly refreshed feed of location records tied to as many as 500 million mobile devices worldwide. In practical terms, that means governments can reconstruct where people live, travel, work, worship, protest, or seek medical care by buying data that originally entered the market through mobile apps and ad-tech pipelines.

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What this article is about

This summary covers The Economist’s March 28th, 2026 China column on page 44, headlined The state of AI and described in the contents as Chaguan AI diffusion.

The article’s core argument is that the most important AI contest may not be who builds the flashiest model, but who is best at spreading the technology through the real economy. On that measure China looks formidable. It has cheap open-source models, a huge manufacturing base, plenty of researchers and, above all, a state willing to push capital and institutions in the same direction. But the article also argues that this same state introduces theatre, caution and bureaucratic drag. China is not simply unleashing AI. It is trying to manage, choreograph and contain it at the same time.

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What this article is really comparing

David Jones’s article starts with a practical question that matters to a lot of pilots right after training: does a pilot really need a dedicated flight computer, or can a phone plus an external Bluetooth vario cover almost everything that matters? The piece is not anti-instrument. It is really an argument against buying complexity by default.

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A safety vacuum hidden in plain sight

Erin Spong’s “Idaho’s Island” opens with a fatal 2021 avalanche in the Big Hole Mountains, where two teenagers were caught without rescue gear in a zone that had dangerous conditions but no dedicated forecast and little established avalanche-awareness culture. That choice of opening does more than provide a dramatic hook. It establishes the article’s central claim: east Idaho’s avalanche problem was not just a string of isolated bad decisions, but a regional blind spot. The terrain was active, the users were out there, and the consequences were real, yet the institutional support that skiers and riders in better-covered zones take for granted had not kept pace.