Small knowledge, big challenge! This article is participating in the creation activity of “Essential Tips for Programmers”.

This article has participated in the “Digitalstar Project” and won a creative gift package to challenge the creative incentive money.

Borrow a big man’s words: for a programmer, the basic knowledge of the computer is internal power, is our professional accomplishment, only deep internal power can walk the river’s lake less.

Programmers can go far, can write high-quality code, can quickly find the bottleneck of the system, can quickly find the core functions of the system, and our professional literacy must be related. Only if you know the basics well enough, can you be truly proficient in your work and solve problems more efficiently and gracefully.

The 408 contains four subjects, including various basic computer theories, even if you do not take the postgraduate entrance examination, it is very good to know some basic knowledge by taking the questions.

🌴 Data structure

If the first root ergodic sequence and the last root ergodic sequence of a binary tree are exactly opposite, the binary tree has the following characteristics: ____ (University of Chinese Academy of Sciences -2018)

A. The height is equal to the number of nodes b. No left child at any node C. No right child at any node D. Empty or with only one nodeCopy the code

parsing

Answer: A,

📢 The order of first root traversal: root-left-right; the order of last root traversal: left-right-root. It can be seen that only the traversal order of the root node changes, while the relative positions of left and right nodes remain unchanged.

In order to satisfy the traversal sequence, which is exactly the opposite, it means that there is no left or right subtree of the whole binary tree, so choose A.

🌳 Computer network

Which of the following digital data encoding methods is self-contained clock encoding? (East China University of Science and Technology, 2006)

A. Binary code B. Non-return to zero code C. Manchester code D. Pulse codingCopy the code

parsing

Answer: C

📢 Manchester encoding divides each symbol into two equal intervals. The first interval being high level and the second interval being low level means that symbol 1 and symbol 0 are the opposite.

The jump in the middle of the bit is both a clock signal and a data signal.

For example, the binary number 10011010 can be expressed as follows. In the figure, the code element is divided into two equal intervals, with the first high and the second low being 1 and the opposite being 0:

🌵 Operating system

___ priority is determined when the process is created and does not change during the entire process (University of Chinese Academy of Sciences, 2015)

A. dynamic B. first come, first served C. short job D. staticCopy the code

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Answer: D

📢 Static priorities are determined when the process is created and do not change for the duration of the process.

As soon as you see a dynamic, you should know that you want to change the state dynamically during runtime 👀

🌲 Computer composition principle

The hamming code is used as the error correction code of a message, and the message is encoded and sent to the receiver. When the encoded message reaches the receiver, an error occurs at bit ___, causing the received message to become 111000111011111. (University of Chinese Academy of Sciences, 2017)

A. 11
B. 13
C. 12
D. 14
Copy the code

parsing

Answer: B

📢 Hamming code is used to correct single-bit errors. Several check bits will be added to the valid information bits to form hamming codes, and the check bits will be placed at 2n, so there are four check bits in the problem:

According to the principle of Hamming code:

Verification check is performed after the analogy:

S4S3S2S1=1011 s_4s_3s_2s_1 = 1011S4S3S2S1=1011.

408 groups have deleted this part of the content, do not need to pay too much attention to 😉

The exercises come from @Wangdao Weibo

The analysis is written by myself, if there are any questions or mistakes, please comment.

I am Mancuoj, welcome to pay attention to me and my computer entrance examination column (≧∇ Blue)