• Analysis and implementation of inverse Polish calculator


    We have completed a reverse Polish calculator, which is required to complete the following tasks: Enter an inverse Polish expression (suffix expression) and use stack to calculate the result Support parentheses and multi digit integers, because here we mainly talk about the data structure, so the calculator is simplified and only supports the calculation of […]

  • Notes on C / C + + Programming: unary operators in C + +! Knowledge points dry goods sharing


    Unary operator:Is an operator that acts on a single number of operands to produce a new value. 1. One dollar minus sign The minus operator changes the sign of its arguments. A positive number becomes a negative number, and a negative number becomes a positive number. int a = 10; int b = -a; // […]

  • Download files using curl command


    Curl is a tool installed by default in UNIX based systems. Curl supports a variety of protocols, including HTTP, HTTPS, FTP, FTPS, SFTP, etc. If you don’t specify any protocol, the default is http. Environmental Science Centos7.7 Download the file to make the name consistent You can use the same name as the curl download […]

  • Chrome can’t play CV2 to extract MP4 video file


    The MP4 source file is intercepted by opencv, and the output is MP4 def clip_video(source_video, target_video, start_time, end_time): cap = cv2.VideoCapture(source_video) if not cap.isOpened(): print(‘video is not opened’) else: success, frame = cap.read() f_shape = frame.shape f_ height = f_ Shape [0] # height of original video picture f_width = f_shape[1] fps = cap.get (5) […]

  • Oracle creates users quickly, imp / exp imports and exports DMP files


    1. First of all, we can use the administrator user to log in to Oracle as SYSDBA sqlplus username/password as sysdba; Then I can create users create user username identified by password; 3. After creating the user, we can modify the user’s password alter user username identified by password; 4. In general, we don’t use […]

  • Linux compression command and decompression script


    suffix tool compress decompression .tar tar tar cvf FileName.tar DirName tar xvf FileName.tar .gz gzip gzip FileName gzip -d FileName.gz .bz2 bzip2 bzip2 -z FileName bzip2 -d FileName.bz2 .Z compress compress FileName compress -d FileName.Z .xz xz xz -z FileName xz -d FileName.xz .zip (un)zip zip FileName.zip DirName unzip FileName.zip .rar rar rar a FileName.rar […]

  • move file


    Do you have trouble moving files? Recursively moves a file with a specified file suffix import os This work adoptsCC agreementReprint must indicate the author and the link of this article If I can, I want to be light

  • C # various file extensions


    .cs: Class moduleCode file. Business logic processing layer code. .sln:Solution fileTo provide solution explorer with the information needed to display the graphical interface of management files. .csproj:Project documentsTo create information about references, data connections, folders, and files needed by the application. .aspx:Dynamic web suffix(Expand: JSP, PHP). (static web page suffixes, such as: HTML, shtml, XML, […]

  • C + + [1] compiling and linking


    Single file example Take single file compilation as an example hello.cc : #include<iostream> using namespace std; int main() { cout << “Hello World” << endl; return 0; } Compiling and running commands g++ ‘hello.cc’ -o ‘hello’ -Wall -g -O2 -std=c++17 && hello The meaning is to put hello.cc The source file is compiled and output […]

  • [Linux]: using archive and compressed package operation in Linux


    1、 The tar command packages files In Linux, the suffix of archive file is tar, and the suffix of compressed package file is tar tar.gz . In Linux, if we want to compress a file, we first need to archive it into tar, and then we can change it into suffix tar.gz The compressed file […]

  • Data structure and algorithm — string


    String Foundation Sequential storage Fixed length array storage: store the actual string length in the 0 th position of the array or use “0” as the terminator. But there is a potential risk in the sequential storage of strings: overflow. Therefore, the storage space of the string can be allocated dynamically. Linked Storage Similar to […]

  • Data structure — generalization structure of tree


    Huffman tree https://www.cnblogs.com/smile… Related concepts 1、The weight of leaf node(weight) is a meaningful numerical quantity given to leaf nodes. 2. Let a binary tree have n weighted leaf nodes. The sum of the product of the path length from the root node to each leaf node and the weight of the corresponding leaf node is […]