2022-11-01：给定一个只由小写字母和数字字符组成的字符串 str。 要求子串必须只含有一个小写字母，数字字符数量随意。 求这样的子串最大长度是多少？

use rand::Rng;fn main() {    let nn: i32 = 100;    let test_time: i32 = 10000;    println!("测试开始");    for _ in 0..test_time {        let n = rand::thread_rng().gen_range(0, nn) + 1;        let str = random_string(n);        let ans1 = right(&str);        let ans2 = zuo(&str);        if ans1 != ans2 {            println!("ans1 = {:?}", ans1);            println!("ans2 = {:?}", ans2);            println!("出错了!");            break;        }    }    println!("测试结束");}
// 一个绝对正确的暴力方法fn right(s: &str) -> i32 {    let str = s.as_bytes();    let mut ans = 0;    for i in 0..str.len() as i32 {        for j in i..str.len() as i32 {            if check(str, i, j) {                ans = get_max(ans, j - i + 1);            }        }    }    return ans;}
fn check(str: &[u8], l: i32, r: i32) -> bool {    let mut letter_number = 0;    for i in l..=r {        if str[i as usize] >= 'a' as u8 && str[i as usize] <= 'z' as u8 {            letter_number += 1;        }    }    return letter_number == 1;}
fn get_max<T: Clone + Copy + std::cmp::PartialOrd>(a: T, b: T) -> T {    if a > b {        a    } else {        b    }}
// 用窗口// 时间复杂度O(N)fn zuo(s: &str) -> i32 {    let str = s.as_bytes();    let n = str.len() as i32;    // 窗口内有几个小写字母了    let mut letters = 0;    // 窗口的右边界    // [left, right)    let mut right = 0;    let mut ans = 0;    // for枚举了每一个窗口的开始位置，0... 1...... 2.....    for left in 0..n {        while right < n {            // right不能越界，一旦越界不用再往右了            if letters == 1 && str[right as usize] >= 'a' as u8 && str[right as usize] <= 'z' as u8            {                break;            }            // letters == 0 str[right]是数字            if str[right as usize] >= 'a' as u8 && str[right as usize] <= 'z' as u8 {                letters += 1;            }            right += 1;        }        // [left.....right)        // [left.....right-1]        if letters == 1 {            ans = get_max(ans, right - left);        }        if str[left as usize] >= 'a' as u8 && str[left as usize] <= 'z' as u8 {            letters -= 1;        }    }    return ans;}
// 为了测试const CHARS: [char; 36] = [    '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i',    'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',];
// 为了测试fn random_string(n: i32) -> String {    let mut ans = String::from("");    for _i in 0..n {        ans.push(CHARS[rand::thread_rng().gen_range(0, 36)]);    }    return ans;}