^= 32 背后的想法是什么，将小写字母转换为大写字母，反之亦然? [英] What is the idea behind ^= 32, that converts lowercase letters to upper and vice versa?

问题描述

我正在解决一些关于 codeforces 的问题.通常我首先检查字符是大写还是小写英文字母，然后减去或添加 32 将其转换为相应的字母.但我发现有人做 ^= 32 做同样的事情.这是:

I was solving some problem on codeforces. Normally I first check if the character is upper or lower English letter then subtract or add 32 to convert it to the corresponding letter. But I found someone do ^= 32 to do the same thing. Here it is:

char foo = 'a';
foo ^= 32;
char bar = 'A';
bar ^= 32;
cout << foo << ' ' << bar << '
'; // foo is A, and bar is a

我已经搜索了对此的解释，但没有找到.那么为什么会这样呢?

I have searched for an explanation for this and didn't find out. So why this works?

推荐答案

我们来看看二进制的ASCII码表.

Let's take a look at ASCII code table in binary.

A 1000001    a 1100001
B 1000010    b 1100010
C 1000011    c 1100011
...
Z 1011010    z 1111010

而 32 是 0100000 这是小写和大写字母之间的唯一区别.所以切换那个位会切换字母的大小写.

And 32 is 0100000 which is the only difference between lowercase and uppercase letters. So toggling that bit toggles the case of a letter.

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