AtCoder Grand Contest 028
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Problem Statement
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You are given $P$, a permutation of $(1,\ 2,\ ...\ N)$.
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A string $S$ of length $N$ consisting of 0 and 1 is a good string when it meets the following criterion:
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- The sequences
$X$and$Y$are constructed as follows: - First, let
$X$and$Y$be empty sequences.- For each
$i=1,\ 2,\ ...\ N$, in this order, append$P_i$to the end of$X$if$S_i=$0, and append it to the end of$Y$if$S_i=$1.
- For each
- If
$X$and$Y$have the same number of high elements,$S$is a good string. Here, the$i$-th element of a sequence is called high when that element is the largest among the elements from the$1$-st to$i$-th element in the sequence.
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Determine if there exists a good string. If it exists, find the lexicographically smallest such string.
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Constraints
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$1 \leq N \leq 2 \times 10^5$$1 \leq P_i \leq N$$P_1,\ P_2,\ ...\ P_N$are all distinct.- All values in input are integers.
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Input
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Input is given from Standard Input in the following format:
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N
P_1 P_2 ... P_N
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Output
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If a good string does not exist, print -1. If it exists, print the lexicographically smallest such string.
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样例
Input #1
6
3 1 4 6 2 5
Output #1
001001
Let $S=$ `001001`. Then, $X=(3,\ 1,\ 6,\ 2)$ and $Y=(4,\ 5)$. The high elements in $X$ is the first and third elements, and the high elements in $Y$ is the first and second elements. As they have the same number of high elements, `001001` is a good string. There is no good string that is lexicographically smaller than this, so the answer is `001001`.
Input #2
5
1 2 3 4 5
Output #2
-1
Input #3
7
1 3 2 5 6 4 7
Output #3
0001101
Input #4
30
1 2 6 3 5 7 9 8 11 12 10 13 16 23 15 18 14 24 22 26 19 21 28 17 4 27 29 25 20 30
Output #4
000000000001100101010010011101
题目信息
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。