See this page.🕗 It contains instructions for each production that needs to be converted: From EBNF to BNF For building parsers (especially bottom-up) a BNF grammar is often better, than EBNF. But it’s easy to convert an EBNF Grammar to BNF: Convert every repetition { E } to a fresh non-terminal X and add X … Read more
This problem can be solved with a recursive combinations of all possible sums filtering out those that reach the target. Here is the algorithm in Python: This type of algorithms are very well explained in the following Stanford’s Abstract Programming lecture – this video is very recommendable to understand how recursion works to generate permutations of solutions. … Read more
I wrote my URL (actually IRI, internationalized) pattern to comply with RFC 3987 (http://www.faqs.org/rfcs/rfc3987.html). These are in PCRE syntax. For absolute IRIs (internationalized): To also allow relative IRIs: How they were compiled (in PHP): Edit 7 March 2011: Because of the way PHP handles backslashes in quoted strings, these are unusable by default. You’ll need … Read more
Bucket sort and radix sort are close cousins; bucket sort goes from MSD to LSD, while radix sort can go in both “directions” (LSD or MSD). How do both algorithms work, and in particular how do they differ?
These following two different 128 byte sequences hash to the same: MD5 Hash: 79054025255fb1a26e4bc422aef54eb4 The differences below are highlighted (bold). Sorry it’s kind of hard to see. d131dd02c5e6eec4693d9a0698aff95c 2fcab58712467eab4004583eb8fb7f89 55ad340609f4b30283e488832571415a 085125e8f7cdc99fd91dbdf280373c5b d8823e3156348f5bae6dacd436c919c6 dd53e2b487da03fd02396306d248cda0 e99f33420f577ee8ce54b67080a80d1e c69821bcb6a8839396f9652b6ff72a70 and d131dd02c5e6eec4693d9a0698aff95c 2fcab50712467eab4004583eb8fb7f89 55ad340609f4b30283e4888325f1415a 085125e8f7cdc99fd91dbd7280373c5b d8823e3156348f5bae6dacd436c919c6 dd53e23487da03fd02396306d248cda0 e99f33420f577ee8ce54b67080280d1e c69821bcb6a8839396f965ab6ff72a70 The visualization of the collision/block1 (Source: Links.Org) The visualization of the … Read more
I hope this qualifies as a programming question, as in any programming tutorial, you eventually come across ‘foo’ in the code examples. (yeah, right?) what does ‘foo’ really mean? If it is meant to mean nothing, when did it begin to be used so?
Yes, Radix Sort and Counting Sort are O(N). They are NOT comparison-based sorts, which have been proven to have Ω(N log N) lower bound. To be precise, Radix Sort is O(kN), where k is the number of digits in the values to be sorted. Counting Sort is O(N + k), where k is the range … Read more
It’s not a matter of which is the best, but of when to use what. In the ‘normal’ cases a simple question is enough to find out if we need inheritance or aggregation. If The new class is more or less as the original class. Use inheritance. The new class is now a subclass of … Read more
Coroutines and concurrency are largely orthogonal. Coroutines are a general control structure whereby flow control is cooperatively passed between two different routines without returning. The ‘yield’ statement in Python is a good example. It creates a coroutine. When the ‘yield ‘ is encountered the current state of the function is saved and control is returned … Read more
See my answer about spatial and temporal locality. In particular, arrays are contiguous memory blocks, so large chunks of them will be loaded into the cache upon first access. This makes it comparatively quick to access future elements of the array. Linked lists on the other hand aren’t necessarily in contiguous blocks of memory, and could … Read more