golang常考的go语言笔试题

计算两个和再打印输出

package main

import (
  "fmt"
  "sync"
)

func sum(a, b int) int {
  var res int
  for i := a; i <= b; i++ {
    res += i
  }
  return res
}

func main() {
  var sum1, sum2 int
  var wg sync.WaitGroup

  wg.Add(2)

  go func() {
    defer wg.Done()
    sum1 = sum(1, 100)
  }()

  go func() {
    defer wg.Done()
    sum2 = sum(101, 200)
  }()

  wg.Wait()

  res := sum1 + sum2
  fmt.Println(res)
}

打印输出字符串

package main

import (
  "fmt"
  "strings"
  "sync"
  "time"
)

func main() {
  var wg sync.WaitGroup
  wg.Add(2)
  str := "hello,world!"
  str1 := []byte(str)
  sc := make(chan byte, len(str))
  count := make(chan int)
  for _, v := range str1 {
    sc <- v
  }
  close(sc)

  go func() {
    defer wg.Done()
    for {
      ball, ok := <-count
      if ok {
        pri, ok1 := <-sc
        if ok1 {
          fmt.Printf("go 2 : %c\n", pri)
        } else {
          close(count)
          return
        }
        count <- ball
      } else {
        return
      }
    }
  }()

  go func() {
    defer wg.Done()
    for {
      time.Sleep(8 * time.Millisecond)
      ball, ok := <-count
      if ok {
        pri, ok1 := <-sc
        if ok1 {
          fmt.Printf("go 1 : %c\n", pri)
        } else {
          close(count)
          return
        }
      } else {
        return
      }
      count <- ball
    }
  }()

  count <- 23
  wg.Wait()
} 

package main

import (
  "fmt"
)

func printString(str string, done chan bool) {
  for _, letter := range str {
    fmt.Printf("%c", letter)
  }
  done <- true
}

func main() {
  done := make(chan bool)

  go printString("Hello", done)
  <-done // 等待第一个goroutine完成

  go printString("World", done)
  <-done // 等待第二个goroutine完成
}

N个协程交替打印1-100

package main

import (
  "fmt"
  "sync"
)

func printer(wg *sync.WaitGroup, ch chan int) {
  defer wg.Done()
  for num := range ch {
    fmt.Println(num)
    ch <- num + 1 // 将下一个数字发送到通道
  }
}

func main() {
  numGoroutines := 5 // 设置协程数量

  var wg sync.WaitGroup
  wg.Add(numGoroutines)

  ch := make(chan int)

  for i := 0; i < numGoroutines; i++ {
    go printer(&wg, ch)
  }

  ch <- 1 // 启动第一个协程开始打印

  wg.Wait()
  close(ch)
}