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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.

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Quick facts

• Difficulty: HARD
• Problem: Median of Two Sorted Arrays
• Main tags: Array, Binary Search, Divide and Conquer

What the problem is really asking

Two arrays are already sorted. If they were merged into one larger sorted array, the task would be to return the middle value.

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Quick facts

• Difficulty: HARD
• Problem: Trapping Rain Water
• Main tags: Array, Two Pointers, Dynamic Programming, Stack

What the problem is really asking

The input is an elevation map where each number is the height of a vertical bar with width 1.

After rain falls, water can sit in the valleys between taller bars. The task is to compute the total amount of water that stays trapped.

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Quick facts

• Difficulty: MEDIUM
• Problem: Container With Most Water
• Main tags: Array, Two Pointers, Greedy

What the problem is really asking

The input is an array of heights. Each height represents a vertical line drawn at that index.

The task is to pick two lines that, together with the x-axis, form a container that holds the most water.

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Quick facts

• Difficulty: MEDIUM
• Problem: Add Two Numbers
• Main tags: Linked List, Math, Recursion

What the problem is really asking

Two linked lists represent two non-negative integers. Each node stores one digit, and the digits are already in reverse order, so the ones place comes first.

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Quick facts

• Difficulty: MEDIUM
• Problem: Longest Substring Without Repeating Characters
• Main tags: Hash Table, String, Sliding Window

What the problem is really asking

Given a string, the goal is to find the length of the longest contiguous block of characters with no repeats.

The important word is contiguous. This is not asking for a subsequence that can skip characters. It is asking for one unbroken window inside the string.

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Quick facts

• Difficulty: MEDIUM
• Problem: Longest Palindromic Substring
• Frequency: 64.1
• Main tags: Two Pointers, String, Dynamic Programming

What the problem is really asking

Given a string, return the longest contiguous substring that reads the same forward and backward.

The word “substring” is the important constraint. This is not about picking scattered characters. The answer has to be one continuous block inside the original string.

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Quick facts

• Difficulty: MEDIUM
• Problem: Subarray Sum Equals K
• Main tags: Array, Hash Table, Prefix Sum

What the problem is really asking

The input is an integer array and a target k.

The task is not to find the longest subarray or to return the subarray itself. It is simply to count how many contiguous subarrays add up to k.