After import x, you can refer to things in x like x.something. After from x import *, you can refer to things in x directly just as something. Because the second form imports the names directly into the local namespace, it creates the potential for conflicts if you import things from many modules. Therefore, the … Read more
Unlike a List<> … A HashSet is a List with no duplicate members. Because a HashSet is constrained to contain only unique entries, the internal structure is optimised for searching (compared with a list) – it is considerably faster Adding to a HashSet returns a boolean – false if addition fails due to already existing … Read more
One problem in your code is cv::threshold which only uses 1 channel images. Finding the pixelwise “difference” between two images in only grayscale often leads to unintuitive results. Since your provided images are a bit translated or the camera wasnt stationary, I’ve manipulated your background image to add some foreground: background image: foreground image: code: … Read more
My own favorites are these two: compare image1 image2 -compose src diff.png compare image1 image2 -compose src diff.pdf The only difference between the 2 commands above: the first one shows the visual difference between the two images as a PNG file, the second one as a PDF. The resulting diff file displays all pixels which … Read more
Relevant article on Programming.Guide: Dynamic programming vs memoization vs tabulation What is difference between memoization and dynamic programming? Memoization is a term describing an optimization technique where you cache previously computed results, and return the cached result when the same computation is needed again. Dynamic programming is a technique for solving problems of recursive nature, … Read more
JVM The Java Virtual Machine (JVM) is the virtual machine that runs the Java bytecodes. The JVM doesn’t understand Java source code; that’s why you need compile your *.java files to obtain *.class files that contain the bytecodes understood by the JVM. It’s also the entity that allows Java to be a “portable language” (write … Read more
rev4: A very eloquent comment by user Sammaron has noted that, perhaps, this answer previously confused top-down and bottom-up. While originally this answer (rev3) and other answers said that “bottom-up is memoization” (“assume the subproblems”), it may be the inverse (that is, “top-down” may be “assume the subproblems” and “bottom-up” may be “compose the subproblems”). … Read more
It uses the C# 4.0 dynamic feature. It achieves the same goal as viewdata and should be avoided in favor of using strongly typed view models (the same way as viewdata should be avoided). So basically it replaces magic strings: ViewData[“Foo”] with magic properties: ViewBag.Foo for which you have no compile time safety. I continue … Read more
I found the best way to do this is with ChronoUnit. long minutes = ChronoUnit.MINUTES.between(fromDate, toDate); long hours = ChronoUnit.HOURS.between(fromDate, toDate); Additional documentation is here: https://docs.oracle.com/javase/tutorial/datetime/iso/period.html
Several possibilities, here’s my favorite library(data.table) setDT(df)[, if(+var(number)) .SD, by = from] # from number # 1: 2 1 # 2: 2 2 Basically, per each group we are checking if there is any variance, if TRUE, then return the group values With base R, I would go with df[as.logical(with(df, ave(number, from, FUN = var))), … Read more