Category Archives: Posts

C++: Unordered maps and sets for non-primitive types

Posted on June 11, 2022 by rendon

Since C++ 11, we can use unordered sets and unordered maps. However, these data structures only seem to work with primitive types and strings. If you need a pair or a vector as the key, you’re out of luck. Fortunately, … Continue reading →

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QuickSelect

Posted on June 11, 2022 by rendon

Theory Quickselect on Wikipedia Implementation in C++ Practice https://leetcode.com/problems/kth-largest-element-in-an-array/

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Fenwick tree (aka Binary Indexed Tree)

Posted on May 30, 2022 by rendon

Theory TopCoder – Binary Indexed Trees Algorithms Live – Fenwick tree Wikipedia – Fenwick tree Implementation in C++ Practice Kattis – Movie collection AtCoder – B Fenwick Tree

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Disjoint Set Union (aka Union-Find)

Posted on May 30, 2022 by rendon

Theory Algorithms, 4th edition by Robert Sedgewick, Kevin Wayne 1.5   Case Study: Union-Find Union Find on Cubits.ai Implementation in C++ Practice https://atcoder.jp/contests/practice2/tasks/practice2_a

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Must read

Posted on May 8, 2022 by rendon

Retries Exponential Backoff And Jitter AWS SDK Retry behavior Error retries and exponential backoff in AWS Example in Java The following example is not meant to be complete, its goal is to give you a good idea of how to … Continue reading →

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Isolate the rightmost (least-significant) bit

Posted on March 27, 2022 by rendon

Fast & elegant: Tests Output Brute force Output for the new version Practice 231. Power of Two 191. Number of 1 Bits Related concepts Two’s complement

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Generate files with random bytes

Posted on March 25, 2022 by rendon

The following command grabs 20 Mb of random bytes from /dev/urandom and saves it to rnd.bin: Generate a bunch of files:

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Kadane’s algorithm

Posted on March 13, 2022 by rendon

I just learned about this algorithm, which is considered a dynamic programming approach. However, depending on the implementation, it might not resemble dynamic programming at all. Check out the implementation presented on Wikipedia: That does not look like dynamic programming … Continue reading →

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AES encryption in Go

Posted on May 1, 2021 by rendon

Here is a program I wrote to learn how to use the Go libraries for AES encryption. Build & run I hope it helps. References Advanced Encryption Standard Advanced Encryption Standard (Wikipedia)

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Build C/C++ libraries with debugging support

Posted on April 30, 2021 by rendon

I’ve been debugging a program which uses certain library on CLion. The IDE is great, but I cannot see most of the code from the library, the debugger shows me assembly code, and that’s not very helpful. The solution was … Continue reading →

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