4 流程控制

1 if 语句

package main

import (
    "fmt"
    "strconv"
)

func test(a int) (res string) {
    if a>=90{
        res = "优"
    }else if a>=80{
        res = "良"
    }else if a >=70{
        res = "中"
    }else if a >=60{
        res = "差"
    }else{
        res = "不及格"
    }
    return
}

func test01()  {
    var a string
    fmt.Scanf("%s",&a)

    res,err := strconv.Atoi(a)
    if err != nil{
        fmt.Println("convert to int err",err)
    }else{
        fmt.Println("you enter is ",res)
    }
}

func main() {
    var a = 55
    fmt.Println(test(a))
}

 2 switch语句

package main

import "fmt"

func switch1() {
    var a = 0

    switch a{
    case 0:
        fmt.Println("a is equal 0")
        //fallthrough  //fallthrough 关键字可以让程序继续往下走
    case 10:
        fmt.Println("a is equal 10")
    default:
        fmt.Println("a is equal other")
    }
}

func switch2()  {
    var a = 3
    switch a{
    case 0,1,2,3,4,5:
        fmt.Println("a equal 0-5")
    case 10:
        fmt.Println("a equal 10")
    default:
        fmt.Println("other")
    }
}

func switch3(){
    var a = 10
    switch {
    case a >0 && a<10:
        fmt.Println("a>0 and a<10")
    case a>=10 && a<20:
        fmt.Println("a>=10 and a <20")
    default:
        fmt.Println("other")
    }
}


func main() {
    switch3()
}

4 猜数字

package main

import (
    "fmt"
    "math/rand"
)

func main() {
    var num = rand.Intn(100)
    var a int
    for{
        fmt.Scanf("%d",&a)
        if isOk(num,a){
            break
        }
    }

}
func isOk(num,a int) (result bool){
    switch  {
    case a>num:
        fmt.Println("大了")
        result = false
    case a < num:
        fmt.Println("小了")
        result = false
    default:
        fmt.Println("猜对了,随机的数字是",num)
        result = true
    }
    return
}

 5 for循环 for range

package main

import "fmt"

func main() {
    //var a = 5
    //for i := 1; i <=a; i++ {
    //    test01(i)
    //}
    test04()
}

//for range语句  可以用来遍历数组,slice,map,chan
func test04() {
    str := "hello world"

    for _,v := range str{
        fmt.Printf("%c\n",v)
    }
}


//无限循环
func test02() {
    for true{

    }

    for {
        fmt.Println("xxx")
    }

}

//for 实现while循环
func test03()  {
    var i = 5
    for i>0{
        fmt.Println(i)
        i--
    }
}

func test01(num int) {
    for i:=1;i<=num;i++{
        fmt.Print("★")
    }
    fmt.Println()

}