leetcode1945&1946

两道题都是字符串的修改。
leetcode上对字符串的考察非常多。
1945

impl Solution {
    pub fn get_lucky(s: String, k: i32) -> i32 {
        let mut t = String::new();
        let mut i = k - 1;
        for c in s.chars() {
            let num = c as i32 - 'a' as i32 + 1;
            t.push_str(&num.to_string());
        }
        while i > 0 {
            let mut sum = 0;
            for c in t.chars() {
                sum += c as i32 - '0' as i32;
            }
            t = format!("{}", sum);
            i = i - 1;
        }
        let mut res = 0;
        for c in t.chars() {
            res += c as i32 - '0' as i32;
        }
        res
    }
}

1946

impl Solution {
    pub fn maximum_number(num: String, change: Vec<i32>) -> String {
        let mut res = String::new();
        let mut begin = 0;
        for c in num.chars() {
            let x = c as i32 - '0' as i32;
            let y = change[x as usize];

            match begin {
                0 => {
                    if y > x {
                        begin = 1;
                        res.push((change[x as usize] as u8 + '0' as u8) as char);
                    } else {
                        res.push((x as u8 + '0' as u8) as char);
                    }
                }
                1 => {
                    if change[x as usize] >= x {
                        res.push((change[x as usize] as u8 + '0' as u8) as char)
                    } else {
                        begin = 2;
                        res.push((x as u8 + '0' as u8) as char);
                    }
                } 
                _ => {
                    res.push((x as u8 + '0' as u8) as char);
                }
            }
        }
        res
    }
}

命令行工具

std::env::args().nth(1).unwrap()可以获取从命令行来的参数，参数从1开始
std::fs::write(path, contents)可以写文件
for item in [a, b, c, d]
items.join("+")用+号把所有项连接起来。
sys.get....