题解 | #查找兄弟单词#

import java.util.*;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    private static List<String> brothers = new ArrayList<>();

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextInt()) { // 注意 while 处理多个 case
            int n = in.nextInt();
            String[] dics = new String[n];
            for (int i = 0; i < n; i++) {
                dics[i] = in.next();
            }
            String word = in.next();
            int index = in.nextInt();
            char[] chars = word.toCharArray();
            // 1 输出可能的兄弟单词，在已提供的字典单词中筛选兄弟单词
            // 1.1 求解单词的可能的兄弟单词：解析出各个字母（含重复字母），按字典序排列组合
            solution(chars, 0);
            brothers.remove(word);
            
            int count = 0;
            List<String> targets = new ArrayList<>();
            for (int i = 0; i < n; i++) {
                if (brothers.contains(dics[i])) {
                    count++;
                    targets.add(dics[i]);
                }
            }
            System.out.println(count);
            // 3 按字典序列输出index的兄弟单词
            String[] targetsInOrder = targets.toArray(new String[]{});
            Arrays.sort(targetsInOrder);
            if (index <= targetsInOrder.length) {
                System.out.println(targetsInOrder[index - 1]);
            } 
        }
    }

    public static void solution(char[] chars, int begin) {
        if (begin >= chars.length) {
            return;
        }
        if (begin == chars.length - 1) {
            brothers.add(String.valueOf(chars));
            return;
        }
        for (int j = begin; j < chars.length; j++) {
            if (checkIfCanSwap(chars, begin, j)) {
                swap(chars, begin, j);
                solution(chars, begin + 1);
                swap(chars, begin, j);
            }
        }
    }

    public static boolean checkIfCanSwap(char[] chars, int begin, int end) {
        for (int i = begin; i < end; i++) {
            if (chars[begin] == chars[end]) {
                return false;
            }
        }
        return true;
    }

    public static void swap(char[] chars, int i, int j) {
        char temp = chars[i];
        chars[i] = chars[j];
        chars[j] = temp;
    }

}