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LeetCode 994: Rotting Oranges
link We let rotting wavefronts emanate from all rotten oranges in each iteration of BFS. As soon as fresh orange count drops to zero we are done. Time: , space: .
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LeetCode 42: Trapping Rain Water
link A bar can hold some water atop if there are left and right supports for it. So, we can compute water on top of each bar and sum up. Time: , space: . We could pre-compute left and right support for each index. Time: , space: . With two pointers moving from two ends,…
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Distributed Cache
Memcache A global, in-memory hash-table distributed across servers. Key and value are strings, item has TTL on top of LRU eviction. Memcache@scale
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Physics: Reading
General Project Course Evolution University Character Lectures By symmetry Noether’s theorem Covariant Mathematician’s pov Geometry Gravitation The book Spacetime Illustrations
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Math: Reading
Calculus Basic concepts Infinite powers Precalculus made difficult Full frontal calculus Calculus Hitchhiker’s Visual complex Visual diff Real saver Probability Fat chance 10 great ideas Intro Lifesaver Art Infinite joy Foundation Linear algebra Dark art Done right Strang Category Conceptual Illustrated And toposes Strings
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LeetCode 1029: Two City Scheduling
link Brute force Try flying each person to city A and city B and take the minimum cost. Time: , space: . Greedy For a cost pair , when we decide to fly a person to city A, we are also deciding to not fly that person to city B. We have to optimize both…
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LeetCode 22: Generate Parentheses
link Valid parentheses have two criteria: We can include “(” if one is available. We cannot close more than opens. So, we include “)” only if enough opens have already been included. Recursive Time: , space: .
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LeetCode 17: Letter Combinations of a Phone Number
link Recursive Letter combinations of “23” is the cartesian product of corresponding letter sets: {“a”, “b”, “c”} and {“d”, “e”, “f”}. Note, there can be at most four different letters for a digit. Time: , space: . Iterative For each possible letter for a new digit, we can append it to each of the earlier…
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LeetCode 46: Permutations
link Recursive Time: , space: . Iterative For a new element , for each earlier permutations, we can insert in different positions to get more permutations. Time: , space: .
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