Score : $300$ points

问题陈述

寻找字符串 $S$ 的所有排列中第 $K$ 个字典序最小的字符串。

什么是字符串的排列？如果字符串 $A$ 中任意字符出现的次数与字符串 $B$ 中相同，那么称字符串 $A$ 是字符串 $B$ 的一个排列。

以上为通义千问 qwen-max 翻译，仅供参考。

Problem Statement

Find the $K$-th lexicographically smallest string among the strings that are permutations of a string $S$.

What is a permutation of a string?A string $A$ is said to be a permutation of a string $B$ when any character occurs the same number of times in $A$ and $B$.

Constraints

• $1 \le |S| \le 8$
• $S$ consists of lowercase English letters.
• There are at least $K$ distinct strings that are permutations of $S$.

Input

Input is given from Standard Input in the following format:

$S$ $K$

Output

Print the answer.

Sample Input 1

aab 2

Sample Output 1

aba

There are three permutations of a string aab: $\{$ aab, aba, baa $\}$. The $2$-nd lexicographically smallest of them is aba.

Sample Input 2

baba 4

Sample Output 2

baab

Sample Input 3

ydxwacbz 40320

Sample Output 3

zyxwdcba

update @ 2024/3/10 09:32:43