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Day 51 - tree problem
2022-07-03 04:35:00 【Adaska】
Start by trying to reduce the dosage , I found that I really can't lie down and fall asleep at night , It really played a great role before , Wake up early , Still feel very uncomfortable , But I still have to adjust my schedule slowly , Don't rely on drugs for too long .
The whole day was spent on Sunday , Maybe because I didn't have a good rest , On Monday night, I didn't feel motivated , In fact, with the problem of brushing and project configuration, it becomes more and more difficult , There is often a sense of frustration , Really overcome the difficulties , Will be happy for a while , But when facing the next problem , Still feel frustrated , It seems that it's not as passionate and fulfilling as it was when it was making rapid progress , I feel a little tired when I get stuck , Maybe this is what we must experience after the normalization of programming , It can't always go well , There will always be problems that are difficult to solve , But anyway , Still face it bravely , Try to persist in solving it .
Today's progress :
1. Insist to take exercise
2. Keep recording the little prince
3. Insist on brushing questions , Keep listening to online classes
4. Keep records
Learning notes :
1.Nginx It's a lightweight model Web The server / Reverse proxy server and email (IMAP/POP3) proxy server , It is characterized by less memory , Strong concurrency , in fact nginx The concurrency ability of is better in the same type of web server , Used in mainland China nginx Website users have : Baidu 、 JD.COM 、 Sina 、 NetEase 、 tencent 、 Taobao, etc. . The reverse proxy server is located between the user and the target server , But for users , The reverse proxy server is equivalent to the target server , In other words, users can get the resources of the target server by directly accessing the reverse proxy server . meanwhile , Users don't need to know the address of the target server , There is no need to make any settings on the client side . A reverse proxy server is usually used as Web Speed up , Use reverse proxy as Web Front end server to reduce network and server load , Improve access efficiency .
2.GCC(GNU Compiler Collection,GNU Compiler Suite ) By GNU Development of programming language translator .GNU The compiler suite includes C、C++、 Objective-C、 Fortran、Java、Ada and Go Language front end , It also includes libraries of these languages ( Such as libstdc++,libgcj etc. .)
3. According to the definition of the free software foundation ,“ The free software ”(Free Software) It refers to those that are given to the user to run 、 Copy 、 distribution 、 Study 、 Modify and improve software these free software .
The meaning of free software , To make users ( Including individuals and groups ) You can control the program for your own use . When the user cannot control the program , Such software is “ non-free ”(Nonfree) or “ proper ”(Proprietary) The program .
4.PCRE(Perl Compatible Regular Expressions Chinese meaning :perl Language is compatible with regular expressions ) It's a use. C Regular expression function library written in language , By Philip . Haize (Philip Hazel) To write .PCRE Is a lightweight function library , Than Boost Regular expression libraries like this are much smaller .PCRE Very easy to use , It's also powerful , The performance is better than POSIX Regular expression library and some classic regular expression libraries
5. Data compression means without losing useful information , Reduce the amount of data to reduce storage space , Improve its transmission 、 Storage and processing efficiency , Or reorganize the data according to a certain algorithm , A technical method to reduce data redundancy and storage space . Data compression includes lossy compression and lossless compression .
6.zlib Function library for data compression , from Jean-loup Gailly And Mark Adler The development of .
7. On the computer network ,OpenSSL Is an open source software library package , Applications can use this package for secure communication , Avoid eavesdropping , At the same time, confirm the identity of the connector at the other end . This package is widely used in web servers on the Internet .
8.SSL yes Secure Sockets Layer( Condom layer protocol ) Abbreviation , Can be in Internet Provide secret transmission on .Netscape The company is launching the first Web At the same time as the browser , Put forward SSL Protocol standard . Its goal is to ensure the security and reliability of communication between two applications , Support can be implemented on both the server and the client . Has become a Internet The industry standard for secure communications .
9.java Use in int n = int(ch) - int(‘0’); Can be char convert to int
10.17. Letter combination of telephone number
Given a number only 2-9 String , Returns all the letter combinations it can represent . You can press In any order return .
The mapping of numbers to letters is given as follows ( Same as phone key ). Be careful 1 Does not correspond to any letter .
Input :digits = “23”
Output :[“ad”,“ae”,“af”,“bd”,“be”,“bf”,“cd”,“ce”,“cf”]
class Solution {
List<String> res = new ArrayList<String>();
String[] map = {
" ", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"};
public List<String> letterCombinations(String digits) {
if(digits.length()==0){
return res;
}
findLetter(digits, 0, "");
return res;
}
public void findLetter(String digits, int index, String tmp){
if(index == digits.length()){
res.add(tmp);
return;
}
char c = digits.charAt(index);
String letter = map[Integer.parseInt(String.valueOf(c))];
for(int i=0; i<letter.length(); i++){
findLetter(digits, index+1, tmp + letter.charAt(i));
}
return;
}
}
Although the matter of changing departments has encountered some twists and turns , It is still advancing normally , In fact, I really want to settle down as soon as possible , But think about it , My situation is just a little better , It's still a long way from the goal , It's so far away that I don't bite my teeth and force myself to accept the reality and give up one day , When you are stuck in difficulties and want to give up , I always think of , No one forced you to do , To change the status quo , I choose to study in my spare time , Don't insist on improving your ability , Is that all you have to do , Still not willing to , So no matter how hard it is , I will also say that I will not try this method anymore , Or insist on doing another problem , So I stumbled all the way , The process of growing up is really hard . Keep going tomorrow !
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