


Detailed explanation of merge sort in PHP sorting algorithm series_php skills
This article mainly introduces the relevant information of the PHP sorting algorithm series Merge Sort in detail. It has a certain reference value. Interested friends can refer to
Merge Sort
Merge sort (MERGE-SORT) is an effective sorting algorithm based on the merge operation. This algorithm is a very typical application of the divide and conquer method (pide and Conquer). Merge the already ordered subsequences to obtain a completely ordered sequence; that is, first make each subsequence orderly, and then make the subsequence segments orderly. If two ordered lists are merged into one ordered list, it is called a two-way merge.
Merge process
The core of merge sort is how to merge two ordered sequences. Assume that there are two ordered arrays and compare the two ordered arrays. Take the first element, whichever is smaller, and put the element into the third array. After taking it, the element will be deleted in the corresponding array, and so on. When an array is fetched and there are no elements, you can Add the remaining elements of the other array directly to the third array.
Principle
1. Merge every two adjacent numbers in the sequence to form ceil(n/2) sequences. After sorting, each sequence contains two elements, the last sequence may have only one element.
2. Merge the above sequences again to form ceil(n/4) sequences. Each sequence contains four elements, and the last sequence may have only three or less elements.
3. Repeat step 2 until all elements are sorted.
Example
Sort the array [53,89,12,6,98,25,37,92,5]
After the first merge
(53,89),12,(6,98),(25,37),(5,92)
After the second merge
(12,53,89),(6,25,37,98),(5,92)
After the third merger
(6,12,25 ,37,53,89,98),(5,92)
After the fourth merger
5,6,12,25,37,53,89,92,98
PHP code implementation
<?php function merge_sort($arr){ $length=count($arr); if($length<=1){ return $arr; } //分解数组,递归排序 $half=ceil($length/2); $arr2=array_chunk($arr,$half); $left=merge_sort($arr2[0]); $right=merge_sort($arr2[1]); while(count($left)&&count($right)){ if($left[0]<$right[0]){ $reg[]=array_shift($left); }else{ $reg[]=array_shift($right); } } return array_merge($reg,$left,$right); }
The above is the entire content of this article. I hope it will be helpful to everyone’s study. I hope everyone will support php Chinese website.
Articles you may be interested in:
Detailed explanation of direct selection sorting of PHP sorting algorithm series
Detailed explanation of insertion sort of PHP sorting algorithm series
Explanation of PHP implementation of bucket sort algorithm
The above is the detailed content of Detailed explanation of merge sort in PHP sorting algorithm series_php skills. For more information, please follow other related articles on the PHP Chinese website!

In PHP, you can use session_status() or session_id() to check whether the session has started. 1) Use the session_status() function. If PHP_SESSION_ACTIVE is returned, the session has been started. 2) Use the session_id() function, if a non-empty string is returned, the session has been started. Both methods can effectively check the session state, and choosing which method to use depends on the PHP version and personal preferences.

Sessionsarevitalinwebapplications,especiallyfore-commerceplatforms.Theymaintainuserdataacrossrequests,crucialforshoppingcarts,authentication,andpersonalization.InFlask,sessionscanbeimplementedusingsimplecodetomanageuserloginsanddatapersistence.

Managing concurrent session access in PHP can be done by the following methods: 1. Use the database to store session data, 2. Use Redis or Memcached, 3. Implement a session locking strategy. These methods help ensure data consistency and improve concurrency performance.

PHPsessionshaveseverallimitations:1)Storageconstraintscanleadtoperformanceissues;2)Securityvulnerabilitieslikesessionfixationattacksexist;3)Scalabilityischallengingduetoserver-specificstorage;4)Sessionexpirationmanagementcanbeproblematic;5)Datapersis

Load balancing affects session management, but can be resolved with session replication, session stickiness, and centralized session storage. 1. Session Replication Copy session data between servers. 2. Session stickiness directs user requests to the same server. 3. Centralized session storage uses independent servers such as Redis to store session data to ensure data sharing.

Sessionlockingisatechniqueusedtoensureauser'ssessionremainsexclusivetooneuseratatime.Itiscrucialforpreventingdatacorruptionandsecuritybreachesinmulti-userapplications.Sessionlockingisimplementedusingserver-sidelockingmechanisms,suchasReentrantLockinJ

Alternatives to PHP sessions include Cookies, Token-based Authentication, Database-based Sessions, and Redis/Memcached. 1.Cookies manage sessions by storing data on the client, which is simple but low in security. 2.Token-based Authentication uses tokens to verify users, which is highly secure but requires additional logic. 3.Database-basedSessions stores data in the database, which has good scalability but may affect performance. 4. Redis/Memcached uses distributed cache to improve performance and scalability, but requires additional matching

Sessionhijacking refers to an attacker impersonating a user by obtaining the user's sessionID. Prevention methods include: 1) encrypting communication using HTTPS; 2) verifying the source of the sessionID; 3) using a secure sessionID generation algorithm; 4) regularly updating the sessionID.


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Dreamweaver Mac version
Visual web development tools

SublimeText3 English version
Recommended: Win version, supports code prompts!

SublimeText3 Mac version
God-level code editing software (SublimeText3)

VSCode Windows 64-bit Download
A free and powerful IDE editor launched by Microsoft

Zend Studio 13.0.1
Powerful PHP integrated development environment
