A hash table is a data structure used to implement an associative array (a structure that can map keys to values). It uses a "hash function" to compute an index into an array from which the value can be found.

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“Invert” a JavaScript object hash whose values are arrays to produce a new object hash with keys as the elements of those original value vectors

Background lodash and underscore have an invert function that takes an object hash and converts it to a new one, which has keys as the input object's values and ...
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log(n) “sort by value” Map<K, V>?

I've read so much arguing about "sort by value maps". Well, I wrote the following log(n) sort by value Map . And, by the way, a real Map , does not allow duplicate keys. Many of the maps I googled ...
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Search strings within a list from strings within a dictionary with the least complexity

I have the following input: newValue = [['men', 'John Doe,Chris perry'], ['women', 'Mary,Anne,Lita']] - list within list ...
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265 views

Data Persistence

I was wondering if I could get some feedback on the library I created to persist data online. JitterPushDemo.java ...
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55 views

An intrusive chained Hash Table

I was interested in experimenting with some intrusive versions of common data structures, so I've written this simple chained hash-table using the approach: ...
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Universal nested get/set for trees in Python

Based on this source, I've made the following universal get / set function, to make it possible to work on OrderedDict trees for example. ...
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Simple Chained HashMap

I am very inexperienced at C++. I wrote a Hash Map which uses chaining for collision resolution. I intentionally did not use smart-pointers, as the objective of this was to learn and showcase. I ...
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Mapping arbitrary Int values to a linear index space

This is part of a growing "primitive" tools collection here on github, and is the initial use-case for the IntArray for review here. Often, when processing data, you encounter unique values that you ...
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Finding all integers in an array with odd occurrence

I am doing an interview exercise problem from here. The problem is to find "all numbers that occurred an odd-number of times in an array". Here is my high level psuedo code thinking: Construct a ...
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75 views

Thread Safe Objects in CSharp - ConcurrentDictionary

I'm using ConcurrentDictionary to hold the records.. I'm reading files from the local system in parallel, to speed up the process. Sample 1: ...
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72 views

Dictionary with restricted keys

I'm currently building some software that works with systemd unit files, and I've been trying to improve how we construct the unit files. This is all running in Python 3.4 This first block is the ...
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120 views

Replace keys in values with key->values from same dictionary

I have a dictionary whose values may contain keys that are already in the dictionary. What we are actually talking about are parameters. Sometimes a parameter is defined by a number plus another ...
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LRU Cache Design using LinkedHashMap

This is a follow-on qestion from: LRU cache design Revised Implementation ...
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Optimizing this method (HashSet.RemoveWhere performance issue)

I have the following method: ...
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BiDirectional Dictionary (and its Mutable friend can come too)

I've attempted to implement a 1-to-1 dictionary in Objective-C. I'm probably missing some convenient methods that one might commonly want to use. These are both declared in the same ...
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Simplifying the code with same list comprehensions

I have such method where: primary_images is dict, additional is ...
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1answer
81 views

Hash table with double hashing

I writing a hash table with double hashing. This code works ONLY with ASCII text files and finding the number of occurrences of each word in input file! Please point out mistakes and shortcomings. ...
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46 views

Use of dictionary for file-saving function

I have the following function: ...
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70 views

VSTO Write Dictionary To Range Extension Method

I was hoping to receive some criticism on this block of code. I wrote it to write the contents of a dictionary to excel range in VSTO. It works well. I am interested to see how people could improve ...
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1answer
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Filtering stocks by dividend yield

I have a dict of stock tickers (KEY) and a data point (VALUE; e.g. dividend yield). I want to know which tickers have a value between a specified min and max value. Given ...
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Optimize huge text file search

I have several huge 100MB text files that I need to scan through to pick out certain frame numbers which relate to a specific log packet of interest. My plan was to scan for these frame numbers and ...
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Hashing a struct in C

I'm trying to learn how chained hashing works, but can't get any further than this. I think hashing works, but after finishing this little program, someone told me that what I have created so far has ...
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1answer
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Handling overwriting of unique Dictionary values

I am working in C# to write a scheduling application for operations in a factory. I have a custom class Workday, with properties to represent a ...
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Hash Table Implemented by Javascript

I recently tried to implement a simple hash table using Javascript. Could anyone help me review my implementation? ...
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118 views

Counting a cycle

An interview question I got - Each element of an int array points to the another element, eventually creating a cycle. Starting at ...
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1answer
52 views

Iterating and fetching values from dictionary

Here is my dictionary: c_result1 = {"1": {"time": "89.46%"}, "2": {"date": "10.54%"}} c_result2 = {"1": {"money": "89.46%"}, "2": {"finance": "10.54%"}} I want ...
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Ruby hashes of status counts

I have a method that takes a model object, reads through its children and returns a hash of status counts. It should only return a count on a status if one exists. This method works, but I was ...
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A double mapped cache with WeakReferences for second key type

I needed a way to cache a large number of objects with two different types of keys. In my case: A String key represents my object in a serialized form. This way ...
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Determining the existence of string Intersections

Problem: Given 2 strings, consider all the substrings within them of length len. Len will be 1 or more. Returns true if there are any such substrings which appear in both strings. Compute ...
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Getting key-value from Object in Java

This takes a collection of Objects from JavaScript and puts them into a Java project. How can I improve this code? What's the best solution? ...
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167 views

Map String to list of string

Input: String : Title; List Tags Problem statement: Need to map title to tags, e.g. title is "china man japan beijing bell" and tags are ...
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Follow-up 2 to Morse Code String

This is my second follow-up. Major changes made: Use a Map instead of an enum for the Morse Characters Added ...
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Recursive Insertion in Hash Table (Linear Probing)

I was practicing implementing a hash function. I tried to use linear probing to insert in hash table. The insertion is working alright but I am not satisfied with the recursion. It doesn't feel like ...
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Finding Facebook Friends on app, and not on app

This code gets all of a user's Facebook friends who use our app and returns a dictionary with keys that are their id's in our database and values that are a default connection level. The code should ...
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122 views

Split a Map into sublists

I may get a Map of many many items that needs to be requested to an API. In order to improve performance, I thought about splitting that list into smaller ...
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128 views

Merge two dict in separate list by id

I have following data structure >>> a = [{'id': 1, 'name': 'a'}, {'id': 2, 'name': 'b'}] >>> b = [{'id': 1, 'age': 12}, {'id': 2, 'age': 21}] I ...
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1answer
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Mapping yielding lots of warnings in use

Recently, I wrote a C header file that defines a new type called HashMap that allows for the storage of key/value pairs. I am just learning about the wonders of ...
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351 views

HashTable implementation

I have been trying to implement the Hash Table function in Java and here is what I came up with. I would just like to get an opinion on this work. Would there be a better way or any improvement to ...
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Hash Binary Tree Map

I made a map based on a binary tree ordered by hashcodes, with collisions fixed with equals(). Are there any improvements I could make? ...
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Regex matching keys in a Dictionary

I have extended this class http://wiki.unity3d.com/index.php/CSharpMessenger_Extended to accept strings containing wildcards as eventTypes, therefore I am able to ...
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Spatial hash triangles from multiple assets

I am implementing the spatial hashing algorithm described in Optimized Spatial Hashing for Collision Detection of Deformable Objects with a few adjustments, the largest one being that each bucket in ...
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Weeding out triangles for triangle-triangle collision detection using a spatial hash

I am implementing a multi-phase collision detection system whose final collision check is checking the triangles of one shape against those of another. As the number of triangle-triangle comparisons ...
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1answer
55 views

Finding average word length in a given year

I have written a function which takes the year in question and words as a data which is a dictionary that maps words to the list of year/count. Now I am wondering how I can improve the code that I ...
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Strategy pattern - design hash table

My programming skill has gotten rusty, so I would like to elicit constructive criticism that can make me write code better. I know the standard design is to use templates, and even obtain the hash ...
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Swift complexities with Dictionary

I have been trying to learn the various aspects of the languages I know so far to do the Daily Challenges in reddit (/r/DailyProgrammer). The one which I am working on just now asks for an ...
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1answer
268 views

Flattening a HashMap of (String → ArrayList) to an ArrayList

I have one HashMap<String, ArrayList<String>> and I want to concatenate a key with every item in its ArrayList. ...
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Sorting array with respect to two properties

I'm sorting with respect to Width and Length. However, Width has the significance ...
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1answer
82 views

Dictionary Key look up with variable length inputs

I am decoding GS1 barcodes and need to match up application identifiers with relevant data about them. ...
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106 views

Convert Object Keys according to Table/Map object

I have implemented a recursive function that converts an object's keys according to another lookup table/map. You are able to convert back and forth using the 3rd ...