Technical weekly | 2021 10 weeks

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🔥 Hi, I’m Chouchou. This article “technology Weekly” – distant glimmer, star sea has been collected, there are Android advanced growth route notes & blog, welcome to grow with Peng Chouchou. (Contact information at GitHub)

• Time stamp of this week: 1615132800 ~ 1615737599
• Progress in 2021:19 percent

Contents of the output

• “The NDK | C review notes”
• The algorithm | calculator series”

NDK

1. Learning content

• C Language Review (100%)

2. Output articles

Algorithms & data structures

1. LeetCode clocks in

• Sunday Punching: 131. Split palindrome string I (Medium)
• Monday Punching: 132. Split Palindromes II (Hard)
• Delete all adjacent duplicates in string (Easy) 【 答 案 】
• A basic calculator I (Hard)
• Thursday Punch: 227. Basic Calculator II (Mediumn)
• Verify the preorder serialization of binary tree (Medium)
• Saturday clock in: 705. Design hash set

2. Output articles

The logical question

Identify the toxic bottle problem

There were 15 bottles, and each bottle was filled with liquid, and at most one of them was toxic. Now there are four mice, and if the mice drink the toxic liquid, they will die after a week.

You have one week to find the poisoned bottle.

• 1, number 1, 2, 3… 15 bottles, converted to binary numbers, for example:1 -> 0001, 2 -> 0010, 3 -> 0011... , 5 - > 1111;
• 2. Four mice correspond to four “binary positions”. If the binary number is 1, the bottle of liquid will be fed to the mice in the corresponding positions;
• 3. One week later, see the state of the mice in the corresponding position and fill in the blanks alive0, hang up1;
• 4. Convert binary to decimal and you get the number of the poisonous bottle.

Android

• Android 12 Developer Preview features (40%)

Further reading

The Distance between No Code and Us. By ISUX

“No Code” refers to the No-code Development Platform (NCDP), which is essentially a graphical user interface that replaces the traditional way programmers write Code line by line. This means that product managers and designers upstream of r&d may need to pay more attention to the impact of the “no code” trend on future product forms than developers do.

Advantages: low threshold, low cost, high efficiency.

In the face of the need to provide non-professional users with a code-free platform design, how to simplify the complexity, grasp the mental model of non-professional users and break out of the thinking habits of professional developers and designers are the challenges that will be encountered in practice.

“Tencent document | digital design” – ISUX

What is the data/how is the data generated: secondary data + survey data + application buried data

Application buried point type: exposure buried point + operation buried point + duration. Based on these three kinds of original data, click rate, functional permeability, per capita click times, per capita use time and other data with comparative value can be calculated.

• Exposure point: the number of times a page or item is displayed;
• Operation buried point: gesture operation (click, double click, long press, slide, etc.) for a certain area (button, card, prompt bar, etc.);
• Time buried point: mark the time difference between the above two types of buried point to obtain.

The role of data analytics in UX design

• 1. Requirements review: evaluate the value contribution and priority of requirements with the goal of improving the final business data;
• 2. Demand mining: data are used as physical examination indicators of product health, and problem domains are delineated for design;
• 3. Design decision: make quick decision on the scheme based on user behavior data;
• 4. Design experiment: Use data experiment to select or improve the design scheme.

How programmers grow up. By Bi Xuan

Programming ability growth:

• Beginner: can use it
• Intermediate: can check and avoid problems
• Advanced: Understands advanced apis and principles

Key points of system design capability:

• 1. Responsibility division of subsystems: in super-large technical solutions, it is easy to overlap and conflict some responsibilities, so how to divide subsystems is very important;
• 2. Control system risk The design of a very large system must be jointly designed by architects in multiple professional fields and large architects. How to ensure that the most important risks of the system can be controlled during the implementation process? In this case, system design principles need to be considered and followed in the design (for example, the basic principle is to accept that the system is not available, but also ensure that the data is consistent).
• 3. Consider the comprehensiveness of the problem: The design of super-large system will involve business level, various basic technical level and infrastructure level, and its execution rhythm also needs to comprehensively consider human input, machine cost, infrastructure layout requirements, stability control, etc.

Key points for system design capability growth:

• 1, now do professional in one or two technical areas, and then try to expand the breadth of their knowledge;
• Practice your ability to do tradeoff.

Beginner’s Mind, by Meng Yan

When we learn something, we don’t just learn something new, we interpret what we read based on what we already know in our head. On the one hand, this will speed up our process of understanding new knowledge, and also help us remember it better, which constitutes compound interest on knowledge. On the other hand, if the new knowledge and the old knowledge are too different, it can also cause us trouble: our brains instinctively resist these conflicts and selectively accept what they think is “reasonable.”

People react differently to new things. Some people are curious about everything, evolving, iterating, and overturning their yesterday selves every day. Some people like a full teacup, no matter what you are talking about when chatting, just want to say what you want to say, for new knowledge instinct rejection.

Pony once said that making products requires the ability to “become white in a second”. If there is no Beginner’s Mind, and they can’t really experience the user’s confusion and problems, but imagine the functions according to their own understanding, the products will have problems.

Technology to share

Kong Gateway Share

Gateway: unified gateway through which external applications access internal interfaces.

Function:

• 1. Access: Take over all API interface services;
• 2. Aggregation: aggregate all back-end business services;
• 3. Intermediary: implement security, authentication, routing, filtering, traffic control, caching and other policies;
• 4, management: provide log, A/B testing, monitoring and other management.

Implementation: Nginx, Kong, SpringCloud, etc

“Normalization algorithm and Its Application” — lecture by Binge

Normalization: compress the value of the data between cells, such as [0,1];

Value:

• Comparability of different indicators
• Improve model accuracy
• Corrected data convergence rate

Implementation:

• Discrete standardization: Y=X −XminXmax−XminY = \frac{x-x_ {min}}{X_{Max} -x_ {min}}Y=Xmax−Xminx−Xmin. The simplest, suitable for data set, XmaxX_{Max}Xmax and XminX_{min}Xmin stable scene;

Z-score 0 Mean normalization: Y=x−μσY = \frac{x – \mu}{\sigma}Y=σx−μ, where μ\muμ is the mean value and σ\sigma sigma is the standard deviation. XmaxX_{Max}Xmax and XminX_{min}Xmin are unknown and need to measure data similarity (classification).

• Sigmoid function: Y = 11 + e – Y = \ frac {1} {1 + e ^ {x} -} Y = 1 + e – x1. Also called logistic regression function, convergence curve is smooth;
• Tanh hyperbolic tangent function: Y = 1 – e + e – 2-2 x1, Y = \ frac {1 – e {- 2 x}} {1 + e ^ {- 2 x}} Y = 1 + 2 x1 – e – e – 2 x. Compared with Sigmoid function, the convergence speed is faster
• ReLU linear rectifier function: y = {x, x > 0 a (ex – 1), x, y = 0 or less \ begin {cases} x, & x > 0 \ \ (^ e x – 1), a & x \ leq0 \ end {cases} y = {x, a (ex – 1), x > 0 x 0 or less. It is a linear function in the interval x>0x >0x>0, and the problem of gradient disappearance of Sigmoid function does not exist.

Application scenario: Sort the list.

Read the extract

Ways of thinking in Economics. Chapter 4. Other Questions about prices. By Thomas Sowell

To understand anything requires first defining it so that it is clear in the mind that it is one thing and not something else that is being discussed. Just as poetic discussions of the weather cannot be regarded as meteorology, moral criticism of the economy or political dogma about it cannot be regarded as economics.

Not finished this week

• Android 12 Developer Preview Features
• Review of the “monotonic queue” problem
• Review of “Program Type Already Present” problem
• The Art of Asking Questions
• Review of the problem of designing hash sets
• Review of static and dynamic linking issues
• C++ basics
• TCP review

Always believe that something wonderful is about to happen!