Programmer Group

OGNL (Object Graph Navigation Language) is an open source expression engine. By using OGNL, we can access arbitrary properties in the Java object tree and call methods of the Java object tree through expressions. In other words, if we regard an expression as a string with semantics, OGNL is the catalyst for the communication between the semant ...

one   virtual function         one point one   definition   The member function decorated with virtual is called   virtual function         one point two   Impact on class memory                 An empty class (there is no data member ...

Level 1: Statistics of user churn Task description This task: according to the user behavior data, write MapReduce program to count the loss of users. Relevant knowledge This training is an intermediate difficulty MapReduce programming exercise, which simulates the statistical analysis of e-commerce data in real scenes. Therefore, it is ...

Chapter 2 sparse arrays and queues 2.1 sparse array 2.1.1 basic introduction When most elements in an array are 0 or the same value array, sparse array can be used to save the array (compress redundant data) Representation of sparse array: How many rows and columns are there in the first row? How many different values are there (relati ...

Fast number theory transformation (NTT) I wanted to learn this thing before. I haven't done it orz. Now I'll make it up. I don't think I have much new knowledge about learning this thing. It's good to master FFT before learning. FFT can be seen here: https://www.cnblogs.com/Tenshi/p/15434004.html NTT is used to solve the modular problem of po ...

To store multiple elements, array is the most commonly used data structure, but array also has many disadvantages: The creation of an array usually requires a continuous memory space, and the size is fixed. Therefore, when the current array cannot meet the capacity requirements, it needs to be expanded (usually apply for a larger array, an ...

Docker MySQL The address of the Docker image of MySQL on the dockerhub: https://hub.docker.com/_/mysql(opens new window) Current (2021-04-02)   latest   and   8.0.23   Is the same mirror. In addition, 5.7   Version and   5.7.33   Is the same mirror. # 1. Installation and test # Query central warehouse docker ...

The world.sql exercise on the mysql official website is used DQL introduction select show Application of select statement select is used alone select @@port; --View port select @@basedir; --View the directory where the program is located select @@server_id; --see server_id mysql> select database(); --View the current library +- ...

Hook rule Use Hook only at the top Do not call Hook in loops, conditions, or nested functions to ensure that they are always invoked at the top level of your React function. By following this rule, you can ensure that hooks are called in the same order in each rendering. This allows react to maintain the correct hook state between multipl ...

Queue learning notes – chain team and sequence team 1. Queue (circular queue) In the sequential storage structure of the queue, in addition to using a group of storage units with continuous addresses to store the elements from the queue head to the queue tail in turn, it is also necessary to attach two integer variable front and rear to ...