The most elegant way to write values in a Map that increase, decrease, or recalculate

The most elegant way to write a value in a Map that increases or decreases automatically or re operates a value without calling get() and put() I believe you can always meet such needs in the process of development: query a key value in the Map, add one if there is one, and put the new key value as 1 if there is no one (or perform other operat ...

Added by Ward on Sat, 19 Feb 2022 02:50:01 +0200

Set framework - Map, set

1, Map interface Key and Value form a mapping relationship by storing data through key and Value • Map Used to save data with mapping relationship, so Map There are two sets of values stored in the collection. One set of values is used to save Map Inside Key , another group is used to save Map Inside Value • Map ...

Added by jokerbla on Mon, 07 Feb 2022 20:12:39 +0200

C++ STL map and multimap

Map and multimap provide methods to operate < key, value > pairs, and store a pair of objects, namely key objects and value objects. Key objects are keys used in the search process, and values are additional data corresponding to keys. For example, if the key is a word, the corresponding value is a number indicating the number of times th ...

Added by aahh on Sat, 29 Jan 2022 07:55:46 +0200

Application of array instance method

Array has many instance methods. Some methods will not change the existing array, but return a new array, and some methods will change the original array. The methods listed in this article are all extracted from real cases of specific projects. 1. forEach Execute the given function once for each element of the array without changing the origi ...

Added by wscreate on Thu, 27 Jan 2022 22:17:58 +0200

[Python] detailed explanation, addition, deletion and modification of dict dictionary

summary Python Dictionary (dict) is an unordered and variable sequence. Its elements are stored in the form of "key value". In contrast, list s and tuple s are ordered sequences, and their elements are stored next to each other at the bottom. The dictionary type is the only mapping type in Python. "Mapping" is a term ...

Added by paulnaj on Mon, 17 Jan 2022 08:25:12 +0200

C + + container - set & map

Content reference: https://www.bilibili.com/video/BV1et411b73Z?p=231 set / multiset container set container Basic concepts Introduction: all elements are automatically sorted when inserted Essence: set / multiset is an associative container, and the underlying structure is implemented by binary tree Difference between set and multiset s ...

Added by nankoweap on Mon, 17 Jan 2022 03:27:48 +0200

Interpretation of HashMap HashTable HashSet source code

A HashMap HashTable HashSet HashMap is a hash table that stores key value mappings. It inherits from AbstractMap and implements Map, Cloneable and Serializable interfaces. The implementation of HashMap is not synchronous, which means that it is not thread safe. Its key and value can be null. The mappings in HashMap are not ordered.  &nbs ...

Added by fred_belanger on Sat, 15 Jan 2022 20:50:55 +0200

swift installation skills: how to use map to generate arrays and write 2 lines less code than for (with demo code)

Let's start with the conclusion: map uses 3 lines of code to solve the problem of 5 lines of code in the for loop, which is equivalent to a 40% increase in efficiency You can't learn without (I said) If you don't use it, you won't be able to use it Because you don't know the usage scenario, you can't use it because you haven't learned it ...

Added by MilesStandish on Fri, 14 Jan 2022 02:57:58 +0200

scala notes -- use WordCount word statistics to explain the functions and differences of map, flatMap and groupBy functions

Using scala implementation, count the number of each word in the file import scala.io.Source object demo14 { def main(args: Array[String]): Unit = { //read file val source = Source.fromFile("Scala/data/words.txt") //Put the read data into a list collection of List[String] type, and each line is used as an element of the li ...

Added by rross46 on Mon, 03 Jan 2022 06:41:20 +0200

Collection, generic, List, Collections, Set, Map

Collection, generic, List, Collections, Set, Map 1, Collection collection 1.1 collection overview Collection: a collection is a container provided in java that can be used to store multiple data. Differences between sets and arrays: The length of the array is fixed. The length of the collection is variable.The elements of the same type are ...

Added by sethcox on Mon, 03 Jan 2022 03:51:41 +0200