我正在做一个URL缩短器,并且正在努力将数字(id)编码为字符串的最佳方法.
I am making an URL shortener, and I am struggling with the optimal way of encoding a number (id) into a character string.
我使用的字符是0-9,A-Z,a-z,因此基本上是base-62编码.那是很基本的,但是并没有利用所有可能的代码.它将产生的代码为:
I am using the characters 0-9,A-Z,a-z so it will basically be a base-62 encoding. That is pretty basic, but it doesn't make use of all possible codes. The codes that it would produce would be:
0, 1, ... y, z, 10, 11, ... zy, zz, 100, 101, ...请注意,未使用代码00到0z,对于000到0zz相同,依此类推.我想使用所有代码,例如:
Notice that the codes 00 to 0z is not used, the same for 000 to 0zz, and so on. I would like to use all the codes, like this:
0, 1, ... y, z, 00, 01, ... zy, zz, 000, 001, ...这将是base-62和base-63的某种组合,根据位置的不同而有所不同...使用base-62很容易,例如:
It would be some combination of base-62 and base-63, with different bases depending on the position... Using base-62 is easy, for example:
create procedure tiny_GetCode @UrlId int as set nocount on declare @Code varchar(10) set @Code = '' while (@UrlId > 0 or len(@Code) = 0) begin set @Code = substring('0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz', @UrlId % 62 + 1, 1) + @Code set @UrlId = @UrlId / 62 end select @Code但是我还没有设法利用它来进行多基转换,以利用所有代码.
But I haven't yet managed to make a multi-base conversion out of it, to make use of all the codes.
推荐答案我设法进行了转换.棘手的是,它不仅是混合的基数转换,而且第一个字符的基数较高还会影响较长代码的值.
I managed to make the conversion. The tricky thing is that it's not just a mixed base conversion, the higher base of the first character also affects the values of longer codes.
我从一个简单的案例开始;以10为基的代码.我看到两位数范围有10个额外的代码,三位数范围有100个额外的代码,依此类推:
I started with an easier case; base-10 codes. I saw that the two digit range has 10 extra codes, the three digit range has 100 extra codes, and so on:
0 - 9 : '0' - '9' 10 - 109 : '00' - '99' 110 - 1109 : '000' - '999' 1110 - 11109 : '0000' - '9999'因此,代码中第一个字符的值不仅是升至该位置的基数,而且还具有偏移量.
So, the value of the first character in the code is not just the base raised to the position, but it also has an offset.
将其应用于base-62编码后,这就是我最终得到的结果:
After applying this to the base-62 encoding, this is what I ended up with:
create function tiny_Encode(@UrlId int) returns varchar(10) as begin declare @Chars varchar(62), @Code varchar(10), @Value int, @Adder int set @Chars = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz' if (@UrlId < 63) begin set @Code = substring(@Chars, @UrlId, 1) end else begin set @UrlId = @UrlId - 1 set @Value = 62 set @Adder = 0 while (@UrlId >= @Value * 63 + @Adder) begin set @Adder = @Adder + @Value set @Value = @Value * 62 end set @Code = substring(@Chars, (@UrlId - @Adder) / @Value, 1) set @UrlId = ((@UrlId - @Adder) % @Value) while (@Value > 1) begin set @Value = @Value / 62 set @Code = @Code + substring(@Chars, @UrlId / @Value + 1, 1) set @UrlId = @UrlId % @Value end end return @Code end更多推荐
多基准转换
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