如何在Golang中找到下一个字符？

问题描述：

I'm just doing some algorithms problems out of interest in golang. I understand that in other languages to find the next character alphabetically I can bitshift the character, as a character (I'm thinking of C) is really a number.

So I tried doing

"a" >> 2

Or something to that effect, but there is a type mismatch.

I'd like to know how I can achieve this.

答

I am not sure where you get the idea that this gives you the 'next character'. This is not true in any language. What 'a' >> 2 does is this:

'a' is interpreted as int32(97) (example)
>> means 'shift X right by Y bits'. Shifting something right by 2 bits is functionally the same as an integer divide by 4. So (x >> 2) == (x / 4). (example)
97 / 4 == 24. The b character has ASCII value 98. So this doesn't get you anywhere near. (example)

More on the bit shifting

Bit shifting is most obvious when considering a number in its binary notation. For the expression z = x >> y, we can note the following:

x(97):  01100001
y(2):   00000010
        -------- >>
z(24):  00011000

Note that all the bits in x have simply been moved to the right by two bits. The 1 that fell off the end is dropped.

Similarly, you can 'shift left' (<<). Just like x >> 1 is the same as x / 2, x << 1 is the same as x * 2.

Expression: 5>>1 == 5/2 == 2:

x(5):   00000101
y(1):   00000001
        -------- >>
z(2):   00000010

Expression: 5<<1 == 5*2 == 10:

x(5):   00000101
y(1):   00000001
        -------- <<
z(10):  00001010

Actually getting the next character

If you want the character directly following 'a', you simply add 1 to it as evidenced in this example.

答

You're trying to shift a string, not a byte, like @Not_a_Golfer said 'a'>>2 should work fine.

However to get the next character you can do something like:

func nextChar(ch byte) byte {
    if ch += 1; ch > 'z' {
        return 'a'
    }
    return ch
}
func main() {
    fmt.Println(string(nextChar('a')))
}

Of course it'd be more complex if you need more than a-z support, take a look at the unicode package and this blog post about go strings.

如何在Golang中找到下一个字符？

More on the bit shifting

Actually getting the next character

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