题解 | #字符串排序#

import java.util.*;

// 硬解，暂时记录一下，后面想到了再优化思路
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while (in.hasNextLine()) {
            String s = in.nextLine();
            System.out.println(sort(s));
        }
    }

    public static String sort(String s) {
        StringBuilder[] bs = new StringBuilder[26];
        char[] cs = s.toCharArray();
        for(int i = 0; i < 26; i++) bs[i] = new StringBuilder();
        int n = s.length();
        ArrayList<Integer> idxs = new ArrayList<Integer>();
        StringBuilder b = new StringBuilder();
        for(int i = 0; i < n; i++) {
            if(!Character.isLetter(s.charAt(i))) continue;
            idxs.add(i);
            int idx = Character.toLowerCase(s.charAt(i)) - 'a';
            bs[idx].append(s.charAt(i));
        }
        for(int i = 0; i < 26; i++) b.append(bs[i]);
        for(int i = 0; i < idxs.size(); i++) cs[idxs.get(i)] = b.charAt(i);
        return new String(cs);
    }
}