如何将单个char转换为int

2022-01-12 00:00:00 char c++

我有一串数字，例如123456789"，我需要提取它们中的每一个以在计算中使用它们.我当然可以通过索引访问每个 char，但是如何将其转换为 int?

I have a string of digits, e.g. "123456789", and I need to extract each one of them to use them in a calculation. I can of course access each char by index, but how do I convert it into an int?

我研究了 atoi()，但它需要一个字符串作为参数.因此，我必须将每个字符转换为字符串，然后在其上调用 atoi.有没有更好的办法?

I've looked into atoi(), but it takes a string as argument. Hence I must convert each char into a string and then call atoi on it. Is there a better way?

推荐答案

你可以利用数字的字符编码都是从 48('0')到 57('9')的顺序.这适用于 ASCII、UTF-x 和几乎所有其他编码(请参阅下面的评论了解更多信息).

You can utilize the fact that the character encodings for digits are all in order from 48 (for '0') to 57 (for '9'). This holds true for ASCII, UTF-x and practically all other encodings (see comments below for more on this).

因此，任何数字的整数值都是数字减去0"(或 48).

Therefore the integer value for any digit is the digit minus '0' (or 48).

char c = '1'; int i = c - '0'; // i is now equal to 1, not '1'

是同义词

char c = '1'; int i = c - 48; // i is now equal to 1, not '1'

但是我发现第一个 c - '0' 更易读.

However I find the first c - '0' far more readable.

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