Digest | 算法：幂集, 一个startup架构

>  2021年04月08日信息消化

### 每天学点算法

#### 幂集 | Power Set

一个集合的幂集是它所有子集的集合。写一个函数，给定一个集合，生成它的幂集。

The power set of a set is the set of all its subsets. Write a function that, given a set, generates its power set.

For example, given the set `{1, 2, 3}`, it should return `{{}, {1}, {2}, {3}, {1, 2}, {1, 3}, {2, 3}, {1, 2, 3}}`.

```python
# https://tutorialspoint.dev/algorithm/mathematical-algorithms/power-set
# python3 program for power set 
  
import math; 
  
def printPowerSet(set,set_size): 
      
    # set_size of power set of a set 
    # with set_size n is (2**n -1) 
    pow_set_size = (int) (math.pow(2, set_size)); 
    counter = 0; 
    j = 0; 
      
    # Run from counter 000..0 to 111..1 
    for counter in range(0, pow_set_size): 
        for j in range(0, set_size): 
              
            # Check if jth bit in the  
            # counter is set If set then  
            # print jth element from set  
            if((counter & (1 << j)) > 0): 
                print(set[j], end = ""); 
        print(""); 
  
# Driver program to test printPowerSet 
set = ['a', 'b', 'c']; 
printPowerSet(set, 3); 
  
# This code is contributed by mits. 
```

## 每天学点Golang

#### 使用GORM和GIN在Golang中实现简单分页功能

原文：[Implement Pagination In Golang Using GORM and GIN](https://medium.com/wesionary-team/implement-pagination-in-golang-using-gorm-and-gin-b4ad8e2932a6)

The packages you need to install in our project is:

```bash
go get github.com/go-sql-driver/mysql
go get github.com/gin-gonic/gin
go get github.com/jinzhu/gorm
```

目录结构

```
- /first-api
	- /Config
  - /Controllers
  - /Model
  - /Routes
  - go.mod
  - go.sum
  - main.go
```

核心分页部分。

- config.go: DB实例

- repo.go

```go
import (
	"first/src/first-api/Config"
	models "first/src/first-api/Model"
)

func GetAllUsers(user *models.User, pagination *models.Pagination) (*[]models.User, error) {
	var users []models.User
	offset := (pagination.Page - 1) * pagination.Limit
	queryBuider := Config.DB.Limit(pagination.Limit).Offset(offset).Order(pagination.Sort)
	result := queryBuider.Model(&models.User{}).Where(user).Find(&users)
	if result.Error != nil {
		msg := result.Error
		return nil, msg
	}
	return &users, nil
}
```

### 其他值得阅读

#### 一个startup架构概览

原文：[Architecture for a startup](https://itnext.io/architecture-for-a-startup-86651962bc99)

- 静态前台（Static web app）：
  -  S3 + CloudFront CDN + Route53
- 后台（Backend production system）
  - EC2（auto-scaling group）+ AWS ElasticCache +  MySQL (RDS) + ALB + Cognito
- 分析（Analytics system）
  - Metabase +  ALB + Cognito
- 监视（Monitoring）
  - NewRelic free tier + self-hosted Sentry server
- 部署（deployment）
  - Jenkins
- Terraform is used for infrastructure as code  
- Ansible is used as configuration management.

#### 我的妈妈在用Arch Linux

原文：[My Mom Uses Arch Linux](https://medium.com/gdg-vit/my-mom-uses-archlinux-e678f29b0df7)

[This gist](https://gist.github.com/L04DB4L4NC3R/90c63f222620758cc069f36ae7354375) covers the whole step-by-step procedure I followed to get it up and running.

- Desktop Environment: *Cinnamon*
- Window Manager: *Mutter*
- File Manager: *Nemo*
- Video Player: mpv
- Image Viewer: *feh*
- Browser: *Firefox*

#### 大规模Vue.js应用的4个最佳实践

原文：[4 Best Practices for Large Scale Vue.js Projects](https://blog.bitsrc.io/4-best-practices-for-large-scale-vue-js-projects-9a533450bdb2)

- Use Vue Slots

- F.I.R.S.T principle： Build & share independent components

- [Bit](https://bit.dev/)

- well organized VUEX Store

```
  └── store
      ├── index.js          
      ├── actions.js
      ├── mutations.js
      └── modules
  ```

- Unit Tests

- Jest, Karma, or Mocha

## 一点收获

- 人生是一场没有赛道的长跑。持续比强度重要。
- GPT-3 learning corpus consists of the common-craw dataset. The dataset includes 45TB of textual data or most of the internet. GPT-3 is 175 Billion parameter models as compared to 10–100 Trillion parameters in a human brain. -- [GPT-3 Explained to a 5-year-old](https://pub.towardsai.net/gpt-3-explained-to-a-5-year-old-1f3cb9fa030b)