去哪儿面试题 （Golang实现）多线程顺序输出1-75

type Num struct {
  val int
  mu  sync.RWMutex
}

func main() {
  num := new(Num)

  wg := sync.WaitGroup{}
  add := func() {
    num.mu.Lock()
    num.val++
    fmt.Println(num.val)
    num.mu.Unlock()
    wg.Done()
  }

  for i := 0; i < 75; i++ {
    wg.Add(1)
    go add()
  }
  wg.Wait()
}

var a struct {

    Mu sync.RWMutex

    Count int

}


var wg sync.WaitGroup


func main()  {

    wg = sync.WaitGroup{}

    wg.Add(75)

    for i:=1; i<=75; i++ {

        go Add()

    }
    wg.Wait()
}

func Add()  {

    defer wg.Done()

    a.Mu.Lock()

    a.Count++

    fmt.Println(a.Count)

    a.Mu.Unlock()

}

输出结果不稳定，也就是说结果不对