2,294 questions
0
votes
0
answers
7
views
How can I insert hashmap values only into Treeset or HashSet
This is my main class:
public class Main {
public static void main(String[] args) throws BookNotFoundException {
// TODO Auto-generated method stub
//Library library = new Library();
...
- 45
0
votes
1
answer
51
views
How can the accuracy of a Bloom filter be improved by introducing other data structures?
Suppose I have a very large dataset (for example, 1 billion keys), and I want to determine if a particular key is in this dataset. In this case, a Bloom filter is a good choice (with a time complexity ...
- 65
0
votes
1
answer
60
views
Is RefCell::as_ptr guaranteed to stay the same for a given RefCell?
I am looking for a way to impl Hash for MyStruct where MyStruct contains `Rc<RefCell> (yes, it's a linked list of a sort).
This answer suggests std::ptr::hash(self.next.as_ref()), but I have ...
- 3
0
votes
0
answers
70
views
how to solve borrowing problem for HashSet
I'm making a tokenizer and have encountered some difficulties.
To better understand the problem, I’ll briefly describe the components of the tokenizer:
Token. There are 3 types - Constant (fixed, ...
0
votes
1
answer
75
views
A hash function that maintains mathematical equality (especially for sets)
I'm working on a little math-based programming language (written in Rust) that uses sets instead of types. In it, a variable or value belongs to a set of values (eg. x : {1, 2, 3} or msg : Str). The ...
- 5
0
votes
1
answer
54
views
Does EFCore Where( ... set.Contains(...)) care whether Set is List or HashSet?
Suppose I an using EFCore to query a SQL DB, and I write:
myTableDbSet.Where(entity => filterSet.Contains(entity.Id))
Then does it make any difference (e.g. to performance) what the concrete type ...
- 8,507
0
votes
2
answers
102
views
What is the time complexity of populating a HashSet with n elements?
I was working on the Leetcode problem "Reverse Vowels of a String."
Here is my first solution:
class Solution {
public String reverseVowels(String s) {
String vowels = "...
- 1
1
vote
1
answer
89
views
Obtaining a Vec<X> from a &HashSet<X> [closed]
Assume I have some function do_stuff that takes a &HashSet<X> and wants to collect the items into a Vec<X> by copying all the elements. What is the canonical way to do that? I have ...
- 274
-1
votes
2
answers
68
views
Why is a HashSet faster than an Array in this Duplicate Integers problem? [duplicate]
I am new to learning data structures and algorithms and am starting NeetCode 150 problems. The first problem I encountered was not difficult, I understand why it works, but I am curious to why the ...
0
votes
1
answer
91
views
C# HashSet but Want to Force Exception When Adding Duplicates
I want to use a HashSet but worry that it "silently" absorbs duplicates (by returning true/false) but not by throwing an Exception. I'm interested in an equivalent data structure that does ...
- 143
0
votes
0
answers
21
views
Unexpected values in HashSet before method invocation in Java
package main;
import java.io.*;
import java.util.*;
public class IsBSTTree {
Set<Integer> set = new HashSet<>();
public static void main(String[] args) throws IOException {...
1
vote
2
answers
82
views
How to build a Set in C# that compares items only by reference equality, instead of HashCode used by HashSet?
For example, what if I want to have a set of strings with different references, allowing them to have the same values?
String s1 = "String1";
String s2 = "String1";
Console....
- 390
0
votes
0
answers
41
views
How is traversal is working on hashsets and hashmaps? [duplicate]
I realize we can use a for loop to iterate over elements of hashset. e.g.
Set set = new HashSet();
for(Object object : set) {
String element = (String) object;
}
I am not able to figure out how ...
0
votes
0
answers
35
views
How to take care of Visited points (in 2D (x,y) ) in Java
In a subproblem, I want to get the total number of points in x-y plane i have visited. and every point must be unique. ie. if you have already visited (1,2) and if you again encounter this you won't ...
1
vote
1
answer
58
views
runtime error because of " unsigned int "
trying to solve 217. Contains Duplicate in C with HashSet.
after i tried to make the calculated index to be always (+) i get an error.
#define BUCKET_SIZE 1000
typedef struct ListNodes {
int val;
...
- 13
0
votes
0
answers
20
views
Xml serialization not working with hashset c# [duplicate]
I have a xml which is using the following structure
<projects>
<project>
<id>1</id>
<pnames>110988</pnames>
</project>
<project>
<...
- 586
0
votes
2
answers
112
views
HashSet: Why valueType.Equals(Object) is so slow
Having this method:
public void RunFD(object fileObj, ISet<object> visited)
{
if (!visited.Add(fileObj)) return;
if (fileObj is IEnumerable enumerablFileObj )
{
foreach (var ...
- 23
-6
votes
1
answer
99
views
Can't print simple HashSet<int[]> elements in java [duplicate]
I try to print simple HashSet in java 20 without success what am i missing here ?
public static void main(String[] args) {
int[] a1 = {1,3,6,8,10,11,14,17,21};
int[] a2 = {2,4,8,9,12,14,15};
...
- 30.9k
0
votes
0
answers
31
views
Fastest way to check if a GUID of set size has been encountered before
There are many questions on checking finding a GUID in a list etc. But I could not find any for just determining if a message was seen before or not.
I have an API which receives requests with a ...
- 2,611
0
votes
1
answer
292
views
Get an Array from HashSet in c# with operator [..]
Are these range operator and indexer? I have never seen them used like this [..h].
Line 6 in this code:
public static void Main(string[] args)
{
int[] a ={1,2,3,4,5,6,7,8,9};
HashSet<int>...
- 11
0
votes
1
answer
32
views
C# Grabbing subset of table based off a Hashset if Ints
I have an Order and OrderMaster table. First I query the Master table, I then create a hashset of a column of Ints from that table. Lastly I want to get all orders that have those values.
When I do ...
- 49
0
votes
0
answers
57
views
Code using ArrayList and HashSet in Java i too slow
I'm trying to solve a problem at open.kattis.com (https://open.kattis.com/problems/lexicography). You get a list of words and an index and you make a list of all the anagrams of the word and return ...
2
votes
1
answer
78
views
Why is my HashSet being serialized incorrectly in ORMLite? It appears to be serialized with the wrong size
I am saving a field in my app as a HashSet<String>, defined as such:
@DatabaseField(dataType = DataType.SERIALIZABLE)
private HashSet<String> allUsers;
Some devices are occasionally ...
- 23
0
votes
1
answer
82
views
Rust ownership for pushing to a vector whose members are referenced
TL;DR: I want a vector of immutable elements that allows for short-lived immutable references to its members, while being able to push to it.
I'm making a crate for exact arithmetic to be used as drop-...
- 736
0
votes
3
answers
105
views
Problem with altering property's value of an object that is inside a HashSet in JAVA [duplicate]
I'm studying java and facing a really weird problem, i think it's easier to explain this along with my code
So this is my class:
class Node
{
private int val;
public Node(int val)
{
...
- 19
2
votes
1
answer
474
views
Efficient way to check if a ReadOnlyMemory<char> contains in a Hashset in C#
I've been looking for some efficient and precise way to check if a ReadOnlyMemory<char> in C# contains in a Hashset of ReadOnlyMemory or any other collection.
I saw some suggestions to convert ...
- 61
0
votes
1
answer
252
views
Difference between a HashSet in C# and HashSet in Java. Any alternatives
I came across this strange behaviour in C# vs Java. The HashSet in Java seems to compare the contents in an object and reject duplicates or gives out a boolean value for when it is checked for ...
- 175
2
votes
0
answers
66
views
CSVHelper doesn't store HashSet fields
I'm working on a software project where the program has a data storage and a UI that lets you manipulate this data. I use multiple data types, some of which contain HashSets. I don't do anything ...
0
votes
1
answer
136
views
Linear probing hash set - efficient way to know if value is already inserted, just not in its hashed index
I am implementing a hash set in C and am using linear probing to deal with collisions. My question is, what happens when you have something like this:
a set with capacity of 32
value a has hash 14, ...
- 402
0
votes
1
answer
69
views
Using clear() vs copy() in a hashset
I was solving this problem on lintcode
I came up with the following solution first and i failed some test cases
from typing import List
class Solution:
def wallsAndGates(self, rooms: List[List[...
- 1,658
1
vote
1
answer
56
views
Searching Time in HashSet vs. Searching Time in TreeSet in Java
I have read that searching time in TreeSet is of the order of log(N) and in HashSet is of the order of 1 (Constant). Now, to test this in a program I have written a Java program.
import java.util....
- 21
-1
votes
2
answers
85
views
Why is a private variable of type HashSet is being shared among object instances of the class? [closed]
I recently stumbled upon this weird behaviour of Java where a variable of type Hashset, which is declared private in the parent class, is not unique for each instance of the child. Instead, all the ...
- 1
0
votes
2
answers
468
views
what difference of hashSetOf() and mutableSetOf() method in kotlin
when or where use hashSetOf() or mutableSetOf() method in kotlin or what difference of these?
I know the hashSetOf() or mutableSetOf() are the mutable but in programming when or where we use them.
val ...
0
votes
1
answer
250
views
Cleanest Way to Get a Set in Redis where Individual Elements Expire in 30 Days?
I need a data structure similar to a Python set in redis, with the additional capability of individual elements automatically expiring (getting popped) from the set 30 days after insertion. Basically, ...
- 1,602
-1
votes
2
answers
122
views
I made a program that should send me two "best phones" from a list of phones in a text file, but only shows one?
This is a link to my java project: https://github.com/Mundanest/Java-files/tree/main/Lab%207
(This is my first time using github, as I'm not sure how else to link a java project folder so I might have ...
- 36
0
votes
0
answers
79
views
Compare a HashSet<string> with an array of strings in LINQ?
I have a List called LabelFilter. Label has a Name field which is just a string such as "Test1" or "Test2" ect. I can easily convert this list into an Array of type string or a ...
- 283
0
votes
1
answer
67
views
What is the difference between hashSet.add(n) and myList.append(n) in terms of Time Complexity? [duplicate]
Starting to leetcode and get Time Exceed Limit error.
Here is the function:
def containsDuplicate(nums: list[int]) -> bool:
tempset = []
for n in nums:
if n in tempset:
...
- 39
1
vote
1
answer
57
views
How to Find best match using hashset(Of String) ignore case
I found the following function to compare text to a list(Of String). Now I want to know if it's possible to make it ignore case in the comparison & if so how would I change this code?
Public ...
-1
votes
1
answer
71
views
How to free the memory of one element in a HashSet?
If I had a code like this:
public class Main {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int n = scanner.nextInt(); //an integer
...
- 9
2
votes
1
answer
125
views
I am using klib library Can i use (khash) KHASH_SET_INIT_INT64() negative values for key. Because i saw in header file its using unsigned long int
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include "klib/khash.h"
KHASH_SET_INIT_INT64(bin_value);
int counter = 1;
int main() {
khash_t(bin_value) *...
- 23
1
vote
0
answers
49
views
How to troubleshoot the performance of a multi-threaded algorithm using a lock-free hashset?
So, I am currently working on graph sampling and developed an algorithm to do this on multiple CPU cores. It uses a lock-free hash set and a locking job queue. Basically, a thread gets a job from the ...
- 225
1
vote
0
answers
21
views
What is the best way to process a vast number of strings keeping unique ones only?
My program produces a very large number (billions) of fixed-size strings (about 110 characters long) from which I want to extract the unique ones, expecting there to be about 100-200 million.
I cannot ...
- 256
0
votes
2
answers
111
views
HashSet iterator() is linear not constant complexity?
I came across that iterator() of HashSet takes too much time. Here is some code example which proves the observation:
import java.text.SimpleDateFormat;
import java.util.*;
import java.util.stream....
- 3
0
votes
1
answer
82
views
How should i store user and user_sessions as HKEY in Redis?
I have Users table which holds passwords, role, profile id and etc. Also i have table User_sessions which holds user_id, session_id, expiry date, user_role and few other data.
Question is i want to ...
0
votes
0
answers
74
views
LeetCode problem 2503 Python optimization
I was trying to solve problem 2503 on LeetCode using Python. I came up with a solution using breadth-first search and a min-heap. However, I ran into time complexity issues with a version of my code. ...
- 11
0
votes
0
answers
100
views
what is faster, std::sort then set_intersection, or std::unordered_map with double for-loop find?
what is a faster?
sort two vectors and then do set_intersection... or
auto intersection = std::make_shared<MediaItems>();
std::sort(m_currentSearchResults->begin(), m_currentSearchResults->...
- 200
3
votes
1
answer
107
views
When does unordered_set invoke operator==?
In my thought,
This was how unordered_set insertion was working.
When insert was called, hash function is called.
In my code below I hash first and second value in pair<string, string> each.
-&...
- 53
3
votes
3
answers
564
views
Compound `HashSet` operations in Rust OR How to get an explicit difference/union of `HashSet`s in Rust
I want perform the following, in pseudocode:
(a, b, c) = (HashSet(...), HashSet(...), HashSet(...))
(a, b, c) = (a - b - c, b - a - c, c - a - b)
In Rust I tried something like this:
fn ...
0
votes
1
answer
167
views
Max Sum in array excluding adjacent numbers
maximum sum of an integer array such that if we consider an element a[i] then we should not consider a[i]-1 and a[i]+1. for example if array a = [1,1,1,1,1,2,2] the o/p = 5 and if a = [3,3,3,4,4,8,1] ...
2
votes
1
answer
269
views
Is it a good practice to instantiate a HashSet from an IEnumerable before using Contains()? [closed]
The piece of code below filters an IEnumerable<T> with another, used as a blacklist. The filtered collection iterates over content fetched remotely (lazy loading, YouTube API).
IEnumerable<...
- 6,314