rust - Rust:最有效的方式来遍历ASCII字符串的字符

Question

我原来的方法:

pub fn find_the_difference(s: String, t: String) -> char {
        let mut c:u8 = 0;
        for i in 0..s.chars().count() {
            c ^= t.chars().nth(i).unwrap() as u8 ^ s.chars().nth(i).unwrap() as u8;
        }
        return (c ^ t.chars().nth(s.chars().count()).unwrap() as u8) as char;
        
    }

但这太慢了，而且还很疯狂，我替换了 t[i] ^ s[i]所需要编写的所有内容(请参见下面的原始C++函数)。因此，我寻找其他东西，找到了 this method，我们在其中将字符串转换为char数组，并获得了一些不错的结果(从8ms变为0ms)。

pub fn find_the_difference(s1: String, t1: String) -> char {
        let mut c:u8 = 0;
        let s: Vec<char> = s1.chars().collect();
        let t: Vec<char> = t1.chars().collect();

        for i in 0..s1.chars().count() {
            c ^= t[i] as u8 ^ s[i] as u8;
        }
        return (c ^ t[s1.chars().count()] as u8) as char;

    }

但是也许不需要收集，也不必关心索引，我只想迭代一个字符。我目前的尝试:

pub fn find_the_difference(s1: String, t1: String) -> char {
        let mut c:u8 = 0;
        let mut s = s1.chars();
        let mut t = t1.chars();
        let n = s.count();
        
        for i in 0..n {
            c ^= t.next().unwrap() as u8 ^ s.next().unwrap() as u8; // c ^= *t++ ^ *s++ translated in C++
        }
        return (c ^ t.next().unwrap() as u8) as char;
        
    }

我收到以下错误消息:

Line 9, Char 44: borrow of moved value: `s` (solution.rs)
   |
4  |         let mut s = s1.chars();
   |             ----- move occurs because `s` has type `std::str::Chars<'_>`, which does not implement the `Copy` trait
5  |         let mut t = t1.chars();
6  |         let n = s.count();
   |                 - value moved here
...
9 |             c ^= t.next().unwrap() as u8 ^ s.next().unwrap() as u8;
   |                                            ^ value borrowed here after move
error: aborting due to previous error

是否可以实现这种代码 c = *t++？
注意:s1.chars.count()= t1.chars.count()-1，目标是在t1中找到多余的字母
NB2:原始的C++函数:

char findTheDifference(string s, string t) {
        char c = 0;
        for (int i = 0; t[i]; i++)
            c ^= t[i] ^ s[i];
        return c;
    }

Answer 1

我认为您对C和Rust字符串处理之间的区别以及Rust的str，String，&[u8]，char和u8类型之间的区别感到困惑。
就是说，这就是我实现您的功能的方式:

fn find_the_difference(s: &[u8], t: &[u8]) -> u8 {
    assert!(t.len() > s.len());
    let mut c: u8 = 0;
    for i in 0..s.len() {
        c ^= s[i] ^ t[i];
    }
    c ^ t[s.len()]
}

如果您的数据当前为 String，则可以使用 &[u8]方法获取其数据的 as_bytes() View 。像这样:

let s: String = ...some string...;
let t: String = ...some string...;

let diff = find_the_difference(s.as_bytes(), t.as_bytes());