go interview questions

There are four threads 1, 2, 3, 4. The function of thread 1 is to output 1, the function of thread 2 is to output 2, and so on... Now there are four files ABCD. Initially empty. Now let's make the four files look like this:

A：1 2 3 4 1 2....

B：2 3 4 1 2 3....

C：3 4 1 2 3 4....

D：4 1 2 3 4 1....

 

In the interview last Friday, the interview gave a go thread question. At that time, I thought of a very stupid way to achieve it. Now I will attach the code after optimization. If there is a better Daniel, you can reply later! ! !

 

package main

import (
    "log"
    "os"
)

func main() {

    a, _ := os.OpenFile("./a.txt", os.O_WRONLY|os.O_APPEND, 0666)
    b, _ := os.OpenFile("./b.txt", os.O_WRONLY|os.O_APPEND, 0666)
    c, _ := os.OpenFile("./c.txt", os.O_WRONLY|os.O_APPEND, 0666)
    d, _ := os.OpenFile("./d.txt", os.O_WRONLY|os.O_APPEND, 0666)
    files := []*os.File{a, b, c, d}
    i := 0
    sign := make(chan int, 1)
    for i < 100 {
        i++
        sign <- 1
        go out1(files[0], sign)
        sign <- 1
        go out2(files[1], sign)
        sign <- 1
        go out3(files[2], sign)
        sign <- 1
        go out4(files[3], sign)

        files = append(files[len(files)-1:], files[:len(files)-1]...)
    }
    a.Close()
    b.Close()
    c.Close()
    d.Close()
}



func out2(f *os.File, c chan int) int {
    f.Write([]byte("2 "))
    // f.Close()
    log.Println(f.Name() + " write finish...")
    <-c
    return 2
}
func out3(f *os.File, c chan int) int {
    f.Write([]byte("3 "))
    // f.Close()
    log.Println(f.Name() + " write finish...")
    <-c
    return 3
}
func out4(f *os.File, c chan int) int {
    f.Write([]byte("4 "))
    // f.Close()
    log.Println(f.Name() + " write finish...")
    <-c
    return 4
}