Professional term

1. data

        Data is a general term for all symbols that can be input into a computer and processed by a computer program .

2. data elements

        Data elements are data Basic unit .

3. Data item

        A data item is a data element Smallest unit .

4. Data objects

        Data object refers to Of the same nature Of Set of data elements .

5. data type

        A data type is a collection of values and some operations defined on the collection of values .

        （ for example ：int ,char,float,double...)

6. Abstract data types （ADT）

        Usually use （ Data objects 、 Data relation 、 Basic operation ） Such triples represent abstract data types .

data structure

         data structure = Logical structure + Storage structure + operation

1. Logical structure ： Refers to the logical relationship between data elements .

        branch 4 Class basic structure ：

        （1） Set structure

        （2） Linear structure （ One to one relationship ）

        （3） A tree structure （ One-to-many relation ）

        （4） A pictorial or reticular structure （ Many to many relationship ）

2. Storage structure （ Also known as physical structure ）： There are mainly sequential storage , Chain store , Index storage , Hash store .

3. operation ： Data operation is an operation algorithm defined on the logical structure of data （ Such as : Additions and deletions ）.

Algorithm

         Algorithm is a description of the solving steps of a specific problem .

Five big characteristic ：

（1） Input ： An algorithm has zero or more inputs ;

（2） Output ： An algorithm has one or more outputs , They are quantities that have a specific relationship to the input ;

（3） deterministic ： Each instruction must have a precise meaning ;

（4） The feasibility of ： The operations described in the algorithm can be realized by available basic operations ;

（5） Fineness ： Algorithm instructions are finite sequences , And the algorithm can be completed in a certain period of time .

  memory ：“ Access is indeed poor ”

Evaluate the advantages and disadvantages of the algorithm Basic standards ：

（1） correctness ： It can ensure the correct output for a certain degree of random input ;

（2） Rapidity ： The algorithm design is reasonable , Efficient execution time , Time complexity can be used to measure ;

（3） Readability ： The algorithm description is clear and easy to understand , Easy to modify and transplant ;

（4） Robustness, ： When entering illegal data , The algorithm can make appropriate response and processing ;

（5） Economy ： The algorithm occupies reasonable storage capacity , Space complexity or storage density can be used to measure .

  memory ：“ Read the key section correctly ”

Algorithm analysis

1. The time complexity of the algorithm ： It refers to the time when the algorithm is executed in the computer The elapsed time The measurement .

    Write it down as ：T(n)=O(f(n)), among n Is the size of the problem .

2. The spatial complexity of the algorithm ： It refers to the time when the algorithm is executed in the computer Storage space The measurement .

    Write it down as ：S(n)=O(f(n)), among n Is the size of the problem .