2022-11-26：给定一个字符串 s，只含有 0~9 这些字符 你可以使用来自 s 中的数字，目的是拼出一个最大的回文数 使用数字的个数，不能超过 s 里含有的个数 比如 : 39878，能拼出的最大回文数是

use std::{cmp::Ordering, collections::HashMap};
impl Solution {    pub fn largest_palindromic(s: String) -> String {        if s == "" {            return String::from("");        }        let mut map: HashMap<i32, i32> = HashMap::new();        let n = s.len() as i32;        let sc: Vec<char> = s.chars().collect();        for i in 0..n {            let number = sc[i as usize] as i32 - '0' as i32;            map.insert(                number,                if map.contains_key(&number) {                    map.get(&number).unwrap() + 1                } else {                    1                },            );        }        let mut heap: Vec<Record> = vec![];        for (k, v) in map.iter() {            heap.push(Record::new(*k, *v));        }        heap.sort_by(compare);        let mut top = heap.remove(0);        if top.times == 1 {            return format!("{}", top.number);        } else if top.number == 0 {            heap.sort_by(compare);            return format!("{}", if heap.len() == 0 { 0 } else { heap[0].number });        } else {            let mut left = String::new();            left.push_str(&format!("{}", top.number));            top.times -= 2;            if top.times > 0 {                heap.push(top);            }            heap.sort_by(compare);            while heap.len() > 0 && heap[0].times > 1 {                top = heap.remove(0);                left.push_str(&format!("{}", top.number));                top.times -= 2;                if top.times > 0 {                    heap.push(top);                }                heap.sort_by(compare);            }            let mut ans = String::new();            ans.push_str(&left);            if heap.len() > 0 {                heap.sort_by(compare);                ans.push_str(&format!("{}", heap[0].number));            }            let lc: Vec<char> = left.chars().collect();            let mut i = left.len() as i32 - 1;            while i >= 0 {                ans.push(lc[i as usize]);                i -= 1;            }            return ans;        }    }}
fn compare(o1: &Record, o2: &Record) -> Ordering {    let l1 = Ordering::Greater;    let l2 = Ordering::Less;
    if o1.times == 1 && o2.times > 1 {        return l1;    }    if o1.times > 1 && o2.times == 1 {        return l2;    }    if o2.number - o1.number > 0 {        return l1;    } else if o2.number - o1.number < 0 {        return l2;    } else {        return Ordering::Equal;    }}
struct Record {    number: i32,    times: i32,}
impl Record {    fn new(n: i32, t: i32) -> Self {        Self {            number: n,            times: t,        }    }}
fn main() {    let ans = Solution::largest_palindromic(String::from("444947137"));    println!("ans = {:?}", ans);}
struct Solution {}