What does linked list in php mean?

In PHP, the linked list is a basic data structure and a linear list; the linked list dynamically allocates storage, can adapt to the dynamic increase and decrease of data, and can easily insert and delete data items. . There are three different types of linked lists: one-way linked lists, doubly linked lists, and circular linked lists.

The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

Linked list in php

Linked list is a common basic data structure. It is a linear list, but it does not store data in a linear order. Instead, it stores data in each node to the next node. Pointer.

The linked list dynamically allocates storage, which can adapt to the dynamic increase and decrease of data, and can easily insert and delete data items. (When inserting or deleting data items in the array, other data items need to be moved, which is very cumbersome.) The linked list must find the next element based on the next pointer.

Using the linked list structure can overcome the shortcoming of the array linked list that the data size needs to be known in advance. The linked list structure can make full use of the computer memory space and achieve flexible dynamic memory management. However, the linked list loses the advantage of random reading of the array, and at the same time, the space overhead of the linked list is relatively large due to the increase of the pointer field of the node.

There are three different types of linked lists: one-way linked lists, doubly linked lists and circular linked lists.

One-way linked list

One-way linked list contains two fields, an information field and a pointer field. This link points to the next node in the list, and the last node points to a null value.

As shown in the picture:

Double linked list

Each node has two connections: one points to the previous one node, (when this "connection" is the first "connection", it points to a null value or an empty list); and the other points to the next node, (when this "connection" is the last "connection", it points to a null value Or an empty list)

As shown in the figure:

Circular linked list

In a circular linked list, the first node and end nodes are connected together. This method can be implemented in both one-way and two-way linked lists. To convert a circular linked list, you start at any node and follow the list in either direction until you return to the starting node. Looking at another method, a circular linked list can be regarded as "headless and tailless". Such lists are useful for conserving data storage caches, assuming you have one object in a list and want all other objects to be iterated over in a non-specific arrangement. The pointer to the entire list may be called an access pointer.

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