生成随机数(纠错)

go标准库:我在其中并没有找到一定要加随机种子的字样
我在其中并没有找到一定要加随机种子的字样
下面这段代码看似随机，但生成就会发现每次都是固定的值
为什么没有产生随机的效果呢？

程序的运行环境是固定的，因此 rand.Intn 总是会返回相同的数字。 （要得到不同的数字，需为生成器提供不同的种子数）

// 这里使用的是“math/rand”
import "math/rand"

func RandInt(min, max int) int {
    if min >= max || min == 0 || max == 0 {
        return max
    }
    return rand.Intn(max-min) + min
}

改正

import "math/rand"

func RandInt(min, max int) int {
    if min >= max || min == 0 || max == 0 {
        return max
    }
    rand.Seed(time.Now().Unix())
    return rand.Intn(max-min) + min
}

根据数组长度生成随机索引

0 第一种

reasons := []string{"85", "89", "45"}
s := mrand.NewSource(time.Now().Unix())
r := mrand.New(s) // initialize local pseudorandom generator
intn := r.Intn(len(reasons))
fmt.Println(intn)

1 第二种

rand.Seed(time.Now().Unix())
mid := codeImei[rand.Intn(len(reasons))]

生成指定长度随机数

import "crypto/rand"

// 注意此处的rand是crypto包下的
func CreateRandomNumber(len int)  string{
    var numbers = []byte{1,2,3,4,5,7,8,9}
    var container string
    length := bytes.NewReader(numbers).Len()

    for i:=1;i<=len;i++{
        random,err := rand.Int(rand.Reader,big.NewInt(int64(length)))
        if err != nil {

        }
        container += fmt.Sprintf("%d",numbers[random.Int64()])
    }
    return container
}

生成随机字符串（随机密码）

import (
    "math/big"
    "bytes"
    "crypto/rand"
    "github.com/go-ffmt/ffmt"
)

func main() {
    randomStr := CreateRandomString(15)
    ffmt.P(randomStr)
    //string("mCvYEd8MH8xnBRn")
}


func CreateRandomString(len int) string  {
    var container string
    var str = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890"
    b := bytes.NewBufferString(str)
    length := b.Len()
    bigInt := big.NewInt(int64(length))
    for i := 0;i < len ;i++  {
        randomInt,_ := rand.Int(rand.Reader,bigInt)
        container += string(str[randomInt.Int64()])
    }
    return container
}

从数组中随机选择

// 此处用的是math/rand
codeImei := []string{"80", "81", "37", "40", "62", "61"}
rand.Seed(time.Now().Unix())
mid := codeImei[rand.Intn(len(codeImei))]

加权随机

现成的轮子

import (
    /* ...snip... */
    wr "github.com/mroth/weightedrand"
)

func main() {
    rand.Seed(time.Now().UTC().UnixNano()) // always seed random!

    chooser, _ := wr.NewChooser(
        wr.Choice{Item: "🍒", Weight: 0},
        wr.Choice{Item: "🍋", Weight: 1},
        wr.Choice{Item: "🍊", Weight: 1},
        wr.Choice{Item: "🍉", Weight: 3},
        wr.Choice{Item: "🥑", Weight: 5},
    )
    /* The following will print 🍋 and 🍊 with 0.1 probability, 🍉 with 0.3
    probability, and 🥑 with 0.5 probability. 🍒 will never be printed. (Note
    the weights don't have to add up to 10, that was just done here to make the
    example easier to read.) */
    result := chooser.Pick().(string)
    fmt.Println(result)
}