T(n): running time of Algo A. We just care about the upper bound and lower bound of T(n) The statement: T(n) >= O(n^2) Upper bound: Because T(n) >= O(n^2), then there’s no information about upper bound of T(n) Lower bound: Assume f(n) = O(n^2), then the statement: T(n) >= f(n), but f(n) could be anything that is “smaller” than n^2 , Ex: constant, n,…, So there’s no conclusion … Read more
SELECT DISTINCT <insert all columns but the PK here> FROM foo. Create a temp table using that query (the syntax varies by RDBMS but there’s typically a SELECT … INTO or CREATE TABLE AS pattern available), then blow away the old table and pump the data from the temp table back into it.
If you’re on .NET 3.5, you can use the following IEnumerable coolness: Edit: and here’s the corresponding VB.NET code: Second edit, in response to remarks that System.Random “isn’t threadsafe” and “only suitable for toy apps” due to returning a time-based sequence: as used in my example, Random() is perfectly thread-safe, unless you’re allowing the routine … Read more
It’s a trick question. If you just want the maximum, (or indeed, the kth value for any k, which includes finding the median), there’s a perfectly good O(n) algorithm. Sorting is a waste of time. That’s what they want to hear. As you say, the algorithm for maximum is really trivial. To ace a question like this, you … Read more
I am meant to create a simple insertion sort method which sorts a series of generic names into alphabetical order. This should be simple, and I have already reviewed many other examples of insertion sort online, including on this site, yet I still cannot seem to obtain the correct output despite comparing my code, line-by-line, … Read more
I am pretty sure most of you know about the minesweeper game. I wanted to code (in C#) my own minesweeper game and was looking for some input as to what would be a good algorithm for that game. I have been browsing over the web for quite some time now but could not find … Read more
Python 3.8+ Python 3.7 and earlier Maybe someone will find this useful (from wikibooks):
In general, the simplest (and quite optimal) algorithm is checking on which side of the half-plane created by the edges the point is. Here’s some high quality info in this topic on GameDev, including performance issues. And here’s some code to get you started:
It can be applied to both. Here is why: An undirected graph is basically the same as a directed graph with bidirectional connections (= two connections in opposite directions) between the connected nodes. So you don’t really have to do anything to make it work for an undirected graph. You only need to know all of the nodes that can be … Read more
There is a better algorithm, which needs at most 6 iterations to converge to maximum precision for double numbers: Algorithm starts with 1 as first approximation for square root value. Then, on each step, it improves next approximation by taking average between current value y and x/y. If y = sqrt(x), it will be the same. If y > sqrt(x), then x/y < sqrt(x) by about the same … Read more