英文:
How to generate a variable length random number in Go
问题
我正在尝试在Go中生成一个长度可变的随机整数,但我总是得到填充了总长度的数字。以下是我的代码:
package main
import (
"fmt"
"math/big"
"crypto/rand"
)
const ResultsPerPage = 30
var (
total = new(big.Int).SetBytes([]byte{
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFE,
0xBA, 0xAE, 0xDC, 0xE6, 0xAF, 0x48, 0xA0, 0x3B, 0xBF, 0xD2, 0x5E, 0x8C, 0xD0, 0x36, 0x41, 0x40,
})
pages = new(big.Int).Div(total, big.NewInt(ResultsPerPage))
random *big.Int
err error
)
func main() {
fmt.Println(pages)
fmt.Println(randomString(pages))
}
func randomString(l *big.Int) string {
random, err = rand.Int(rand.Reader, l)
fmtrandom := fmt.Sprint(random)
return string(fmtrandom)
}
输出结果:
3859736307910539847452366166956263595094585475969163479420172104717272049811
3479662380009045046388212253547512051795238437604387552617121977169155584415
代码示例:https://play.golang.org/p/HxAb6Rs_Uj
感谢任何帮助。谢谢。
英文:
I'm trying to generate a random integer with variable length in Go but I always get the number filling the total length. Here's my code:
package main
import (
"fmt"
"math/big"
"crypto/rand"
)
const ResultsPerPage = 30
var (
total = new(big.Int).SetBytes([]byte{
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFE,
0xBA, 0xAE, 0xDC, 0xE6, 0xAF, 0x48, 0xA0, 0x3B, 0xBF, 0xD2, 0x5E, 0x8C, 0xD0, 0x36, 0x41, 0x40,
})
pages = new(big.Int).Div(total, big.NewInt(ResultsPerPage))
random *big.Int
err error
)
func main() {
fmt.Println(pages)
fmt.Println(randomString(pages))
}
func randomString(l *big.Int) string {
random, err = rand.Int(rand.Reader, l)
fmtrandom := fmt.Sprint(random)
return string(fmtrandom)
}
Outputs
3859736307910539847452366166956263595094585475969163479420172104717272049811
3479662380009045046388212253547512051795238437604387552617121977169155584415
Code sample: https://play.golang.org/p/HxAb6Rs_Uj
Any help is appreciated. Thank you.
答案1
得分: 2
如果我理解正确,你遇到的问题是随机数似乎总是与允许的最大值具有相同的位数,对吗?当我运行代码时,情况并非如此。这是我刚刚观察到的输出:
3859736307910539847452366166956263595094585475969163479420172104717272049811
65719900872761032562423535702578352960653752260368991759410130265294153783
在 playground 中,我相信随机种子和时钟时间是固定的,所以你会反复看到相同的结果。但在本地运行时,我看到了预期的输出长度变化。
更新
你可能想知道为什么你可以多次运行这段代码,并观察到随机数的长度很常常接近最大值的长度。
一点数学可以解释这个问题。让我们想象我们在0到999之间选择一个数字。在这个范围内有多少个数字:
- 有3位数?900个(100-999)
- 有2位数?90个(10-99)
- 有1位数?10个(0-9)
类似地,对于你的非常大的最大值,大多数可以选择的数字将非常接近该最大长度。很少会看到比该长度短两位数的数字。(你应该大约1%的时间看到它们。)
英文:
If I understand correctly, the issue you're having is that the random number appears to always have the same number of digits as the maximum allowed value, right? When I run the code, this is not the case. Here's an output I just observed:
3859736307910539847452366166956263595094585475969163479420172104717272049811
65719900872761032562423535702578352960653752260368991759410130265294153783
In the playground, I believe the random seed and clock time are fixed, so you'll see the same result repeatedly. But running locally, I see the expected variation in the length of the output.
UPDATE
You may wonder why you can run this code a bunch of times and observe that the length of the random number is very often close to the length of the maximum value.
A little math explains this. Let's imagine we're picking a number between 0 and 999. How many numbers in that range have:
- 3 digits? 900 (100-999)
- 2 digits? 90 (10-99)
- 1 digit? 10 (0-9)
Similarly, with your very large maximum value, most of the numbers that can be picked will be very close to that maximum length. It will be rare to see a number two digits short of that length. (You should see them on the order of 1% of the time.)
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