I wrote the following modern C++20 pipeline to filter records returned by a database query helper function: #include <iostream> #include <vector> #include <ranges>std::vector<int> getTemperatures() { return {18, 25, 32, 14, 29, 36}; }int ...Read more
RTSALL Latest Questions
Given a characters array tasks representing the tasks a CPU needs to do, and a cooldown integer n, each task takes 1 CPU interval. Identical tasks must be separated by at least n cooldown intervals. Most people simulate this using a ...Read more
Given an array of integers nums and an integer k, return the total number of subarrays whose sum equals k. Many people try to use a Sliding Window / Two Pointers approach, but it fails whenever the array contains negative numbers. ...Read more
We are building a distributed task build engine (similar to Bazel or Make) that resolves dependency trees across 500,000 code packages. Textbooks teach both Kahn’s algorithm (indegree BFS) and DFS post-order reversal. Why do production build systems almost universally prefer Kahn’s ...Read more
When sharding key-value data across distributed cache nodes (like Redis or Memcached clusters), the naive approach is hash(key) % N, where N is the number of servers. The fatal flaw is that adding or removing a single server changes N, causing ...Read more
The standard DP solution for Longest Increasing Subsequence (LIS) uses two nested loops: for each element i, scan all previous elements j < i. That takes O(N^2) time, which times out when N = 100,000. Everyone says the optimal solution is ...Read more
When implementing Dijkstra’s algorithm for large road networks (millions of nodes and edges), the standard textbook approach pushes a new pair (new_dist, u) into a binary heap whenever a shorter path is found. This means old, obsolete distance pairs remain sitting ...Read more
We are building an in-memory session cache for an API gateway handling 50k requests/sec. We need an LRU (Least Recently Used) cache where both get() and put() operations happen strictly in O(1) time. A lot of implementations I see online either ...Read more