


PHP implements finding the entry node of the ring in the linked list
This article explains PHP implementation to find the entry node of the ring in the linked list.
A linked list contains a ring, please find the entry node of the ring in the linked list.
Solution ideas
The first step is to find the intersection point in the ring. Use p1 and p2 to point to the head of the linked list respectively. p1 takes one step each time and p2 takes two steps each time until p1==p2 finds the intersection point in the ring.
The second step is to find the entrance to the ring. Continuing from the previous step, when p1==p2, the number of nodes passed by p2 is 2x, and the number of nodes passed by p1 is x. Assume there are n nodes in the ring, and p2 walks one more circle than p1, so 2x=n x; n=x ; It can be seen that p1 actually takes the number of steps of a ring, and then lets p2 point to the head of the linked list. The position of p1 remains unchanged. p1 and p2 take one step at a time until p1==p2; At this time, p1 points to the entrance of the ring. (I still don’t understand it very well)
Implementation code
/*class ListNode{ var $val; var $next = NULL; function __construct($x){ $this->val = $x; } }*/ function EntryNodeOfLoop($pHead) { if($pHead == null || $pHead->next == null) return null; $p1 = $pHead; $p2 = $pHead; while($p2!=null && $p2->next!=null){ $p1 = $p1->next; $p2 = $p2->next->next; if($p1 == $p2){ $p2 = $pHead; while($p1!=$p2) $p1 = $p1->next; $p2 = $p2->next; } if($p1 == $p2) return $p1; } } return null; }
This article explains the PHP implementation of finding the entry node of the ring in the linked list. For more related content, please pay attention to the PHP Chinese website.
Related recommendations:
php nginx real-time output implementation method
PHP Class SoapClient not found processing method
How to implement the mongoDB singleton mode operation class in php
The above is the detailed content of PHP implements finding the entry node of the ring in the linked list. For more information, please follow other related articles on the PHP Chinese website!

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

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

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

Hot Topics

PHP 8.4 brings several new features, security improvements, and performance improvements with healthy amounts of feature deprecations and removals. This guide explains how to install PHP 8.4 or upgrade to PHP 8.4 on Ubuntu, Debian, or their derivati

If you are an experienced PHP developer, you might have the feeling that you’ve been there and done that already.You have developed a significant number of applications, debugged millions of lines of code, and tweaked a bunch of scripts to achieve op

Visual Studio Code, also known as VS Code, is a free source code editor — or integrated development environment (IDE) — available for all major operating systems. With a large collection of extensions for many programming languages, VS Code can be c

JWT is an open standard based on JSON, used to securely transmit information between parties, mainly for identity authentication and information exchange. 1. JWT consists of three parts: Header, Payload and Signature. 2. The working principle of JWT includes three steps: generating JWT, verifying JWT and parsing Payload. 3. When using JWT for authentication in PHP, JWT can be generated and verified, and user role and permission information can be included in advanced usage. 4. Common errors include signature verification failure, token expiration, and payload oversized. Debugging skills include using debugging tools and logging. 5. Performance optimization and best practices include using appropriate signature algorithms, setting validity periods reasonably,

A string is a sequence of characters, including letters, numbers, and symbols. This tutorial will learn how to calculate the number of vowels in a given string in PHP using different methods. The vowels in English are a, e, i, o, u, and they can be uppercase or lowercase. What is a vowel? Vowels are alphabetic characters that represent a specific pronunciation. There are five vowels in English, including uppercase and lowercase: a, e, i, o, u Example 1 Input: String = "Tutorialspoint" Output: 6 explain The vowels in the string "Tutorialspoint" are u, o, i, a, o, i. There are 6 yuan in total

This tutorial demonstrates how to efficiently process XML documents using PHP. XML (eXtensible Markup Language) is a versatile text-based markup language designed for both human readability and machine parsing. It's commonly used for data storage an

Static binding (static::) implements late static binding (LSB) in PHP, allowing calling classes to be referenced in static contexts rather than defining classes. 1) The parsing process is performed at runtime, 2) Look up the call class in the inheritance relationship, 3) It may bring performance overhead.

What are the magic methods of PHP? PHP's magic methods include: 1.\_\_construct, used to initialize objects; 2.\_\_destruct, used to clean up resources; 3.\_\_call, handle non-existent method calls; 4.\_\_get, implement dynamic attribute access; 5.\_\_set, implement dynamic attribute settings. These methods are automatically called in certain situations, improving code flexibility and efficiency.
