AtCoder Regular Contest 136
A
A ↔ BB
AtCoder
⌀ 0
原题
←B →
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Problem Statement

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You are given a string $S$ of length $N$ consisting of A, B, C.

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You can do the following two kinds of operations on $S$ any number of times in any order.

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  • Choose A in $S$, delete it, and insert BB at that position.
  • Choose two adjacent characters that are BB in $S$, delete them, and insert A at that position.
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Find the lexicographically smallest possible string that $S$ can become after your operations.

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What is the lexicographical order? Simply speaking, the lexicographical order is the order in which words are listed in a dictionary. As a more formal definition, here is the algorithm to determine the lexicographical order between different strings $S$ and $T$. Below, let $S_i$ denote the $i$-th character of $S$. Also, if $S$ is lexicographically smaller than $T$, we will denote that fact as $S \lt T$; if $S$ is lexicographically larger than $T$, we will denote that fact as $S \gt T$. Let $L$ be the smaller of the lengths of $S$ and $T$. For each $i=1,2,\dots,L$, we check whether $S_i$ and $T_i$ are the same. If there is an $i$ such that $S_i \neq T_i$, let $j$ be the smallest such $i$. Then, we compare $S_j$ and $T_j$. If $S_j$ comes earlier than $T_j$ in alphabetical order, we determine that $S \lt T$ and quit; if $S_j$ comes later than $T_j$, we determine that $S \gt T$ and quit. If there is no $i$ such that $S_i \neq T_i$, we compare the lengths of $S$ and $T$. If $S$ is shorter than $T$, we determine that $S \lt T$ and quit; if $S$ is longer than $T$, we determine that $S \gt T$ and quit.

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Constraints

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  • $1 \leq N \leq 200000$
  • $S$ is a string of length $N$ consisting of A, B, C.
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Input

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Input is given from Standard Input in the following format:

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N
S

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Output

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Print the answer.

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样例

Input #1
4
CBAA
Output #1
CAAB
We should do the following. - Initially, we have $S=$`CBAA`. - Delete the $3$-rd character `A` and insert `BB`, making $S=$`CBBBA`. - Delete the $2$-nd and $3$-rd characters `BB` and insert `A`, making $S=$`CABA`. - Delete the $4$-th character `A` and insert `BB`, making $S=$`CABBB`. - Delete the $3$-rd and $4$-th characters `BB` and insert `A`, making $S=$`CAAB`. We cannot make $S$ lexicographically smaller than `CAAB`. Thus, the answer is `CAAB`.
Input #2
1
A
Output #2
A
We do no operation.
Input #3
6
BBBCBB
Output #3
ABCA
题目信息
题号
arc136_a
时间限制
2 s
内存限制
1024 MB

题面与样例版权归 AtCoder 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。