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MEDIUMHash Table, String, BacktrackingEach digit from 2 to 9 maps to a small set of letters, just like an old phone keypad. Given a string of digits, the task is to return every possible letter string that could be formed by choosing one mapped letter for each digit.
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MEDIUMArray, Two Pointers, SortingThe surface task is to return every unique quadruplet whose sum equals target.
The harder part is not the arithmetic. It is avoiding duplicate answers while still searching efficiently.
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MEDIUMArray, BacktrackingThe input contains distinct integers, and the task is to return every possible ordering of those integers.
That means the algorithm is not trying to find one best answer. It is trying to systematically explore a decision tree where:
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MEDIUMArray, Math, MatrixThe input is an n x n matrix, and the task is to rotate it 90 degrees clockwise.
The important constraint is that the rotation must happen in place. That means the matrix itself must be rearranged without allocating another full n x n matrix for the final answer.
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MEDIUMString, Dynamic ProgrammingTwo strings are given, word1 and word2.
The goal is to transform word1 into word2 using as few operations as possible. The allowed operations are:
This is not a greedy string-matching problem. A locally good edit can make the rest of the string worse, so the real challenge is deciding which prefixes of the two words should be matched together.
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MEDIUMArray, Two Pointers, SortingThe input array contains only 0, 1, and 2. Those values represent three categories, and the goal is to reorder the array in place so all 0s come first, then all 1s, then all 2s.
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Robin George Andrews frames the article as a report from the end of an unusually successful planetary mission. Juno was sent to Jupiter to answer an old question with modern tools: what does the solar system’s largest planet really look like beneath its clouds, and what can that tell scientists about how the solar system formed? Instead of filling in a few gaps, the spacecraft seems to have broken much of the old picture.
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Techmeme surfaced this story in its April 13, 2026 roundup, and the original article is Stanford HAI’s The 2026 AI Index Report.
Stanford’s latest AI Index argues that the biggest mistake right now is to think AI progress is flattening out. The report says the opposite is happening: frontier capability is still improving quickly, adoption is spreading across organizations and consumers, and the center of gravity is moving from isolated model launches toward a broader system built from chips, datacenters, capital, education, and public policy.
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This summary covers The Economist’s March 28th, 2026 Business article listed in the contents under Social media and headlined Big tech's reckoning.
The article argues that a California jury verdict against Meta and Google matters not because the damages are large, but because the legal theory is new. Instead of blaming the companies for specific harmful posts, the case attacks the addictive design of the platforms themselves. That gives critics a way around the legal shield that has protected social-media firms for years.
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Calef Letorney’s article argues that “active piloting” is often invoked as a vague compliment or criticism when it should be treated as a concrete, trainable discipline. The core idea is simple: a paraglider should not be allowed to wander through the sky while the pilot passively endures whatever the air does next. A good pilot is constantly feeling what the wing is doing, predicting where it is about to go, and making timely corrections that keep the glider overhead and efficient. Letorney frames that work not as nervous overcontrol but as the normal operating mode of serious paragliding.
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