自定义基数列(+特殊字符) [英] Custom radix columns (+special characters)

问题描述

目前我正在使用此代码将数字转换为 base36 字符串:

Currently I'm using this code to convert a number into an base36-string:

let number = 300293338
let base36 = String(number, radix: 36);
print(base36) // 4ysbtm

但我想知道如何使用 Swift 通过一种 Base10 到 AnyBase 的转换来生成我自己的字母表.

But I'm wondering how it's possible to generate my own alphabet with a kind of a Base10 to AnyBase conversion using Swift.

字母表的一个例子可能是这样的:

An example of the alphabet could be something like this:

["$", "%", "&", "/", "(", "9", "=", "?", "+", "#", "-", ".", ">", "<", "*", "!", ...]

它可能看起来像这样:

let number = 300293338
let base36 = mycoolfunction(number)
print(base36) // "$%//+#="

推荐答案

如何使用基本的基数 10 到任何基数转换，修改自定义数字:

How about using the basic base 10 to any base conversion, modified for custom digits:

func numberToCustomRadix(_ number: Int, alphabet: String) -> String {
    let base = alphabet.count
    var number = number
    var result = ""
    repeat {
        let idx = alphabet.index(alphabet.startIndex, offsetBy: number % base)
        result = [alphabet[idx]] + result
        number /= base
    } while number > 0
    return result
}

numberToCustomRadix(3, alphabet: "012") // 10
numberToCustomRadix(4, alphabet: "abc") // bb
numberToCustomRadix(5, alphabet: "%#9") // #9

请注意，自定义字母表的问题在于，在编译时很难保证字母表包含不同的字符.例如.aaabbbccc"字母表会产生各种转换问题.

Note that the problem with a custom alphabet is the fact that it's hard to guarantee at compile time that the alphabet contains distinct characters. E.g. an "aaabbbccc" alphabet will generate all kind of conversion problems.

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