Basic concepts

The three elements of data structure

1、 Logical structure of data

（1） aggregate
（2） Linear structure

① There is a one-to-one relationship between data elements
② Except for the first element , All elements have unique precursors
③ Except for the last element , All elements have a unique successor

（3） A tree structure

There is a one to many relationship between data elements

（4） Figure structure （ Network structure ）

There is a many to many relationship between elements

2、 Storage structure of data

(1) Sequential storage

Store logically adjacent elements in a physical location that is also adjacent to each other , The relationship between elements is represented by the adjacency of storage units

(2) Chain store

Logically adjacent elements are not adjacent maliciously in physical location , The logical relationship between elements is represented by the pointer of element storage address

(3) Index storage

While storing element information , Also create additional index tables , Each item in an index table is called an index entry , The general form of an index entry is :( keyword , Address )

(4) Hash store

According to the key words of the element, the storage address of the element can be calculated directly , Also known as hash (Hash) Storage

notes ：
（1） If sequential storage is used , Each data element must be physically continuous ; If non sequential storage is used , Then each data element can be physically dispersed .
（2） The storage structure of data will affect the convenience of storage space allocation
（3） The storage structure of data will affect the speed of data operation

3、 The operation of data