set

问题 I'll go first. I'm 100% in the set-operations camp. But what happens when the set logic on the entire desired input domain leads to a such a large retrieval that the query slows down significantly, comes to a crawl, or basically takes infinite time? That's one case where I'll use a itty-bitty cursor (or a while loop) of perhaps most dozens of rows (as opposed to the millions I'm targeting). Thus, I'm still working in (partitioned sub) sets, but my retrieval runs faster. Of course, an even

问题 I'm trying to accomplish some animation with sets in Raphael, but even though an opacity animation worked, I cannot succeed in moving a set (or even a circle) around the canvas. I found on the Web that moving a set should be done with setting translation, not x, y positions (as they may be different for each element in the set, and just x and y may not be enough for moving some elements), but it doesn't work for me. Nothing is moving, even though the animation callbacks are executed in time,

问题 In Java I have a set where I want to obtain all possible combinations of subsets which their union make the main set. (partitioning a set) for example, given: set={1,2,3} the result should be: { {{1,2,3}} , {{1},{2,3}} , {{1,2},{3}} , {{1,3},{2}}, {{1},{2},{3}}} the number of possible partition of a set of n elements is B(n) known as Bell number. The code so far: public static <T> Set<Set<T>> powerSet(Set<T> myset) { Set<Set<T>> pset = new HashSet<Set<T>>(); if (myset.isEmpty()) { pset.add

问题 I have this input of type "file" , and I want to change its files list. Example: <input type = "file" id = "fileinput" /> <script type = "text/javascript> document.getElementById("fileinput").files = [10]; </script> The problem is that the fileinput element's files list is not set. How do I do it? 回答1: For security reasons, browsers prevent javascript from changing the files which will be uploaded: only the user can select files via the user interface. This is to prevent an evil script to

问题 This question already has answers here : Python set class, float and int evaluation (1 answer) Why is bool a subclass of int? (3 answers) Closed last year . I just started investigating the set data type in Python. For some reason, whenever I add the Boolean value of True to a set it doesn't appear. However, if I add False to a set it will become an element of the set. I was shocked when I googled this question that nothing came up. example1 = {1, 2, 7, False} example2 = {7, 2, 4, 1, True}

问题 I have 2 different instances of HashMap I want to merge the keysets of both HashMaps; Code: Set<String> mySet = hashMap1.keySet(); mySet.addAll(hashMap2.keySet()); Exception: java.lang.UnsupportedOperationException at java.util.AbstractCollection.add(AbstractCollection.java:238) at java.util.AbstractCollection.addAll(AbstractCollection.java:322) I don't get a compile warning or error. From java doc this should work. Even if the added collection is also a set: boolean addAll(Collection c) Adds

问题 In calculate if two arbitrary regular expressions have any overlapping solutions (assuming it's possible). For example these two regular expressions can be shown to have no intersections by brute force because the two solution sets are calculable because it's finite. ^1(11){0,1000}$ ∩ ^(11){0,1000}$ = {} {1,111, ..., ..111} ∩ {11,1111, ..., ...11} = {} {} = {} But replacing the {0,1000} by * remove the possibility for a brute force solution, so a smarter algorithm must be created. ^1(11)*$ ∩

问题 I have the following kind of situation: Set<Element> set = getSetFromSomewhere(); if (set.size() == 1) { // return the only element } else { throw new Exception("Something is not right.."); } Assuming I cannot change the return type of getSetFromSomewhere() , is there a better or more correct way to return the only element in the set than Iterating over the set and returning immediately Creating a list from the set and calling .get(0) 回答1: You can use an Iterator to both obtain the only

问题 If I have a string, and want to create a set that initially contains only that string, is there a more Pythonic approach than the following? mySet = set() mySet.add(myString) The following gives me a set of the letters in myString : mySet = set(myString) 回答1: In 2.7 as well as 3.x, you can use: mySet = {'abc'} 回答2: For example, this easy way: mySet = set([myString]) 回答3: For Python2.7+: set_display ::= "{" (expression_list | comprehension) "}" Example: >>> myString = 'foobar' >>> s =

问题 I have a simple collections question. I have a Set<String> object. I want an enumeration of the strings in that set. What is the cleanest/best way to go about it? 回答1: EDIT: There's no need to write your own (although I'll leave the implementation below for posterity) - see Kevin Bourrillion's answer for the one in the JDK. If you really need an enumeration, could could use: Enumeration<String> x = new Vector(set).elements(); It would be better to use Iterable<E> if at all possible though...