Score : $200$ points

问题描述

给定一个字符串 $S$，找出通过重新排列 $S$ 的字符得到的字典序最小的字符串 $S'$。

这里，对于两个不同的字符串 $s = s_1 s_2 \ldots s_n$ 和 $t = t_1 t_2 \ldots t_m$，若满足以下任一条件，则认为 $s \lt t$ 在字典序上成立：

• 存在一个整数 $i\ (1 \leq i \leq \min(n,m))$，使得 $s_i \lt t_i$ 并且对于所有整数 $j\ (1 \leq j < i)$，都有 $s_j=t_j$。
• 对于所有整数 $i\ (1 \leq i \leq \min(n,m))$，有 $s_i = t_i$，并且 $n \lt m$。

以上为通义千问 qwen-max 翻译，仅供参考。

Problem Statement

You are given a string $S$. Find the lexicographically smallest string $S'$ obtained by permuting the characters of $S$.

Here, for different two strings $s = s_1 s_2 \ldots s_n$ and $t = t_1 t_2 \ldots t_m$, $s \lt t$ holds lexicographically when one of the conditions below is satisfied.

• There is an integer $i\ (1 \leq i \leq \min(n,m))$ such that $s_i \lt t_i$ and $s_j=t_j$ for all integers $j\ (1 \leq j \lt i)$.
• $s_i = t_i$ for all integers $i\ (1 \leq i \leq \min(n,m))$, and $n \lt m$.

Constraints

• $S$ is a string of length between $1$ and $2 \times 10^5$ (inclusive) consisting of lowercase English letters.

Input

Input is given from Standard Input in the following format:

$S$

Output

Print the lexicographically smallest string $S'$ obtained by permuting the characters in $S$.

Sample Input 1

aba

Sample Output 1

aab

Three strings can be obtained by permuting aba:

• aba
• aab
• baa

The lexicographically smallest among them is aab.

Sample Input 2

zzzz

Sample Output 2

zzzz

update @ 2024/3/10 10:25:00