Reading Standard Input (StdIn) in Swift

Hello! A nice partner. If you have tried some of the Hackerrank assignments as Swift as your preferred language, this may be a way to provide test case input in Hackerrank, so reading input from StdIn may be encountered.

In most languages, just get the boilerplate code and write the logic, just select swift as the language and it looks like this.

One option is to create a MacOS -> Command Line Tools application, but if you are only used to the iOS app, it will take some time to fix it. Let's stick to the playground, which is fun for us.

However, readLine () always returns nil in the playground. How can I test it? Do not worry, I will come to that part. First, let's look at the logic necessary to read the Hackerrank input.

Since there is always a Hackerrank input value, you can use enforceable line breaks here. However, please do not do this with the production code.

Problem description: Consider two strings, and perhaps the same length or different strings, to determine the minimum number of characters and crossword puzzle required to make a puzzle. You can delete any character from any string

Please write your solution on the playground. Please note that the playground encounters nil of readLine () so it displays an error. You can provide default values ​​to protect it or to provide a solution, and you can return it to the readLine () code when you are ready to paste it into Hackerrank's editor.

Now, to test it, save it as a preferred location for the Anagram.swift file. Move to that location on the terminal and enter the following:

Hello! You are ready to hand Hackerrank code right away. Once ready, test with a few different inputs, comment out all print logs except the final answer, paste them into Hackerrank to run and test them.

But it shows effective programming decisions: What do we accept from standard input and what do you accept from users? There is no easy answer, but if you think about it, you may already have it. Program structured input (init file format, html, structured data etc) comes from stdin. Manual input (prompt, query etc) comes from userin. The same problem applies to standard output and user output. My instinct is telling me that this is not a complicated decision. Use userout whenever you feel you need to write stderr, but that does not mean an error. Standard output is the output of your program, there is no change. User output is explicitly output to user

When displaying information or entering commands on the screen, the computer does this in a way called standard stream. Therefore, when you enter a command, the command is processed and sent via standard input (standard input), then sent via standard output (standard output) or standard error (standard output). Cat file1.txt file2.txt file3.txt // Printing multiple files at once Another way to display the contents of a file on the screen is to use more or less commands. To print on one page To print a file with too much content, use the more command to split the file into multiple pages. In a nutshell, you can scroll down, but you can not scroll up. The less command works the same way, but it has some functions, but we will not explain it here. I do not want to lengthen this part.

After calling dup2, the descriptor stdin points to the file foo. All reads to stdin are read from file foo (this also applies to fd read, but it closes immediately as it is not used). This setting of stdin is saved by execvp and the program bar is executed with standard input connected to file foo. This is how the shell executes commands like bar <foo. After calling dup2, the descriptor stdout points to the file foo. All writes to stdout are written to the file foo (this also applies to writing to fd, but it closes immediately as it is not used). This setting of stdout is reserved by execvp and the program bar is connected to the file foo with standard output. This is how the shell executes commands like bar> foo.

Please think about the program you have to write. Since you are a real Unixer, it accepts input from stdin output to stdout. It has beautiful simplicity, which further strengthens the pipeline. The pipeline is really beautiful. It is not a joke. They are conceptually meaningful and wonderful concepts. There is not much to have this. "The two mistakes are incorrect, as long as you are not Chuck Norris, the round house will kick your face with two mistakes." And the IP, the request and response to the title, as well as the progress bar I also replied. Finally, the output is passed to jq, where you can jest in a fun way.