hashset

问题 I'm writing an A.I. to solve a "Maze of Life" puzzle. Attempting to store states to a HashSet slows everything down. It's faster to run it without a set of explored states. I'm fairly confident my node (state storage) implements equals and hashCode well as tests show a HashSet doesn't add duplicate states. I may need to rework the hashCode function, but I believe what's slowing it down is the HashSet rehashing and resizing. I've tried setting the initial capacity to a very large number, but

问题 I am relatively new to Java and am puzzled about the following thing: I usually add objects to an ArrayList before setting its content. I.e., List<Bla> list = new ArrayList<>(); Bla bla = new Bla(); list.add(bla); bla.setContent(); // content influences hashCode This approach works great. I am concerned whether this approach will give me trouble when used with HashSet s or HashMap s. The internal hash table get set at the time the object is added. What will happen if setContent() gets called

问题 I have this code: public class Tray { private Set<Block> blocks; private int numColumns; private int numRows; //constructor public Tray (int numRows, int numColumns){ this.numColumns = numColumns; this.numRows = numRows; blocks = new HashSet<>(); } public boolean satisfiesGoal(Tray other){ Block thisBlock = this.blocks.iterator().next(); Block otherBlock = other.blocks.iterator().next(); boolean hashesEqual = thisBlock.hashCode() == otherBlock.hashCode(); // this is true boolean areEqual =

问题 So what I know is that a HashSet has no real sorting capabilities like a SortedSet, however I stumbled upon this : When I run the following code : public static void main(String[] args) { Set<String> collection = new HashSet<String>(2000); String[] data = {"a", "c", "g", "f", "b", "f", "b", "d","q","r","d","m"}; for(String input: data) { collection.add(input); } System.out.println("Output: " + collection); } I get the following output : Output: [a, b, c, d, f, g, m, q, r] Which is

问题 I have a std::collections::HashSet , and I want to sample and remove a uniformly random element. Currently, what I'm doing is randomly sampling an index using rand.gen_range , then iterating over the HashSet to that index to get the element. Then I remove the selected element. This works, but it's not efficient. Is there an efficient way to do randomly sample an element? Here's a stripped down version of what my code looks like: use std::collections::HashSet; extern crate rand; use rand:

问题 I have to use a HashSet where a lot of duplicate value may be inserted. But I want to preserve the earlier data inserted in the hash when a later insertion makes the duplicate. To examine this I have write the following code and insert many duplicate value, but it doesn't satisfy me. Please see the code below - import java.util.HashSet; import java.util.Set; public class SetTest { private static Set<Student> studentSet = new HashSet<Student>(); private static Student s1, s2, s3, s4, s5, s6,

问题 I have to use a HashSet where a lot of duplicate value may be inserted. But I want to preserve the earlier data inserted in the hash when a later insertion makes the duplicate. To examine this I have write the following code and insert many duplicate value, but it doesn't satisfy me. Please see the code below - import java.util.HashSet; import java.util.Set; public class SetTest { private static Set<Student> studentSet = new HashSet<Student>(); private static Student s1, s2, s3, s4, s5, s6,

问题 I have a hashmap that maps strings keys to hashsets values, and I want to remove a key from the hashmap when the hashmaps's hashset value is empty. I'm having trouble approaching this. Here's what I've tried but I'm very stuck: for(Map.Entry<String, HashSet<Integer>> entr : stringIDMap.entrySet()) { String key = entr.getKey(); if (stringIDMap.get(key).isEmpty()) { stringIDMap.remove(key); continue; } //few print statements... } 回答1: In order to avoid ConcurrentModificationException, you need

问题 Looking at this question it made me curious as to which to use, Hashset vs ArrayList. The Hashset seems to have a better lookup and ArrayList has a better insert (for many many objects). So I my question is, since I can't insert using an ArrayList, then search through it using a HashSet, I'm going to have to pick one or the other. Would inserting with an ArrayList, converting to a HashSet to do the lookups, be SLOWER overall than to just insert into a HashSet then lookup? Or just stick with

问题 I stumbled upon the following problem. I want a hashset with all numbers from 1 to 100.000.000. I tried the following code: var mySet = new HashSet<int>(); for (var k = 1; k <= 100000000; k++) mySet.Add(k); That code didn't make it since I got memory overflow somewhere around the 49mil. This was also pretty slow and memory grew excessively. Then I tried this. var mySet = Enumerable.Range(1, 100000000).ToHashSet(); where ToHashSet() is the following code: public static HashSet<T> ToHashSet<T>