1610372700

# Cấu trúc dữ liệu và thuật toán #15: Queue Code | DS&A

Hế lô hế lô, Ông dev đây!
Cấu trúc dữ liệu và thuật toán #15: Queue Code bao gồm:

• CircularArrayBasedQueue
• So sánh performance

Source code: https://github.com/OngDevTutorials/ds-a-tut

#developer #programming

1610372700

## Cấu trúc dữ liệu và thuật toán #15: Queue Code | DS&A

Hế lô hế lô, Ông dev đây!
Cấu trúc dữ liệu và thuật toán #15: Queue Code bao gồm:

• CircularArrayBasedQueue
• So sánh performance

Source code: https://github.com/OngDevTutorials/ds-a-tut

#developer #programming

1604008800

## Static Code Analysis: What It Is? How to Use It?

Static code analysis refers to the technique of approximating the runtime behavior of a program. In other words, it is the process of predicting the output of a program without actually executing it.

Lately, however, the term “Static Code Analysis” is more commonly used to refer to one of the applications of this technique rather than the technique itself — program comprehension — understanding the program and detecting issues in it (anything from syntax errors to type mismatches, performance hogs likely bugs, security loopholes, etc.). This is the usage we’d be referring to throughout this post.

“The refinement of techniques for the prompt discovery of error serves as well as any other as a hallmark of what we mean by science.”

• J. Robert Oppenheimer

### Outline

We cover a lot of ground in this post. The aim is to build an understanding of static code analysis and to equip you with the basic theory, and the right tools so that you can write analyzers on your own.

We start our journey with laying down the essential parts of the pipeline which a compiler follows to understand what a piece of code does. We learn where to tap points in this pipeline to plug in our analyzers and extract meaningful information. In the latter half, we get our feet wet, and write four such static analyzers, completely from scratch, in Python.

Note that although the ideas here are discussed in light of Python, static code analyzers across all programming languages are carved out along similar lines. We chose Python because of the availability of an easy to use `ast` module, and wide adoption of the language itself.

### How does it all work?

Before a computer can finally “understand” and execute a piece of code, it goes through a series of complicated transformations:

As you can see in the diagram (go ahead, zoom it!), the static analyzers feed on the output of these stages. To be able to better understand the static analysis techniques, let’s look at each of these steps in some more detail:

### Scanning

The first thing that a compiler does when trying to understand a piece of code is to break it down into smaller chunks, also known as tokens. Tokens are akin to what words are in a language.

A token might consist of either a single character, like `(`, or literals (like integers, strings, e.g., `7``Bob`, etc.), or reserved keywords of that language (e.g, `def` in Python). Characters which do not contribute towards the semantics of a program, like trailing whitespace, comments, etc. are often discarded by the scanner.

Python provides the `tokenize` module in its standard library to let you play around with tokens:

Python

1

``````import io
``````

2

``````import tokenize
``````

3

4

``````code = b"color = input('Enter your favourite color: ')"
``````

5

6

``````for token in tokenize.tokenize(io.BytesIO(code).readline):
``````

7

``````    print(token)
``````

Python

1

``````TokenInfo(type=62 (ENCODING),  string='utf-8')
``````

2

``````TokenInfo(type=1  (NAME),      string='color')
``````

3

``````TokenInfo(type=54 (OP),        string='=')
``````

4

``````TokenInfo(type=1  (NAME),      string='input')
``````

5

``````TokenInfo(type=54 (OP),        string='(')
``````

6

``````TokenInfo(type=3  (STRING),    string="'Enter your favourite color: '")
``````

7

``````TokenInfo(type=54 (OP),        string=')')
``````

8

``````TokenInfo(type=4  (NEWLINE),   string='')
``````

9

``````TokenInfo(type=0  (ENDMARKER), string='')
``````

(Note that for the sake of readability, I’ve omitted a few columns from the result above — metadata like starting index, ending index, a copy of the line on which a token occurs, etc.)

#code quality #code review #static analysis #static code analysis #code analysis #static analysis tools #code review tips #static code analyzer #static code analysis tool #static analyzer

1605188700

## Cấu trúc dữ liệu và thuật toán #2: Thuật toán là gì? | DS&A

Hế lô hế lô, Ông dev đây!
Video này mình sẽ nói về thuật toán:

• Thuật toán là gì
• Tại sao phải phân tích thuật toán
• Các yếu tố khi phân tích một thuật toán
• Tại sao phân tích thời gian chạy của một thuật toán
• Các kiểu dữ liệu khi phân tích

Source code: https://github.com/OngDevTutorials/ds-a-tut

#developer #programming

1608817500

## Cấu trúc dữ liệu và thuật toán #13: Queue | DS&A

Hế lô hế lô, Ông dev đây!
Cấu trúc dữ liệu và thuật toán #13 mình sẽ giới thiệu cho các bạn về Stack

• Queuelà gì
• Các loại Queue
• Các method của Queue ADT
• Các ứng dụng của Queue

Source code: https://github.com/OngDevTutorials/ds-a-tut

#developer #programming

1605534300

## Cấu trúc dữ liệu và thuật toán #3: BigO Notation và ví dụ | DS&A

Hế lô hế lô, Ông dev đây!
Cấu trúc dữ liệu và thuật toán #3 này mình sẽ nói về BigO Notation và đưa ra một số ví dụ:

• BigO là gì
• BigO để làm gì
• Các thuộc tính trong BigO
• Ví dụ và cách tính BigO

Source code: https://github.com/OngDevTutorials/ds-a-tut

#developer #programming