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Dancing Links
Here is a demonstration of the Dancing Links idea (Wikipedia definition). The idea is this: if you remove an item from a doubly-linked list, you can put it right back in as long as you hold on to it....
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Aho-Corasick String Matching Dictionary
This is an implementation of the Aho-Corasick String Matching Dictionary (Wikipedia). This algorithm lets you search for (all instances of) multiple substrings in a single pass through the haystack....
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2-Dimensional String Search
In my previous two posts, I implemented KMP search with continuation and the Aho-Corasick dictionary. Now we can put it all together and perform a 2D search, finding a rectangular needle in a larger...
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Quick Union Find
Let’s say you have 9 vials of liquid and the list of pairs to combine as follows: 1 & 2 (new batch) 5 & 8 (new batch) 9 & 4 (new batch) 9 & 6 (new 6 goes into existing 9) 3 & 5 (new...
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Exact Cover Problem and Knuth’s Algorithm X
I‘ve put together an implementation of Knuth’s Algorithm X (Wikipedia), which solves the Exact Cover problem (Wikipedia). The example from Algorithm X’s Wikipedia page is as follows: Set Set Set Set...
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Binary-Indexed Tree
A Binary-Indexed Tree is a standard array with extra range indexes, and looks like the following: Each single cell (shown as an empty square on each row) is an array item, indexed from [1, n]. Each...
View ArticleKosaraju’s Algorithm
Kosaraju’s algorithm (Wikipedia) finds a graph’s strongly connected components in linear time. The algorithm runs in two phases: Phase 1: grab an unseen node and perform depth-first search. add node to...
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