最后一个单词长度

/// 复习API
pub fn length_of_last_word(s: String) -> i32 {
    s.split_whitespace().last().unwrap().len() as i32
}

计算某字符出现次数

千万注意！！！！
数组的ASCII码嵌入在字母中！！！

fn main() {
    let mut buff = String::new();
    std::io::stdin().read_line(&mut buff).unwrap();
    let mut tar = String::new();
    std::io::stdin().read_line(&mut tar).unwrap();
    let res = count_sum_char(buff, tar);
    println!("{}", res);
}
fn count_sum_char(s: String, tar: String) -> i32 {
    let mut count = 0;
    let tar = tar.chars().next().unwrap() as usize;
    let cut = 'a' as usize - 'A' as usize;
    let num_t = '9' as usize;
    let num_d = '1' as usize;
    s.chars().for_each(|c| {
        let c = c as usize;
        // 数字是种特殊情况
        if tar>=num_d && tar<=num_t {
            if c == tar { count += 1; }
        }else {
            if c == tar || c == (tar+cut) || c == (tar - cut){
                count += 1;
            }
        }
    });
    count
}