Codeforces Round 934 (Div. 2)
C
MEX Game 1
Codeforces
未评级
原题
← BD →
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Alice and Bob play yet another game on an array $a$ of size $n$. Alice starts with an empty array $c$. Both players take turns playing, with Alice starting first.

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On Alice's turn, she picks one element from $a$, appends that element to $c$, and then deletes it from $a$.

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On Bob's turn, he picks one element from $a$, and then deletes it from $a$.

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The game ends when the array $a$ is empty. Game's score is defined to be the MEX$^\dagger$ of $c$. Alice wants to maximize the score while Bob wants to minimize it. Find game's final score if both players play optimally.

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$^\dagger$ The $\operatorname{MEX}$ (minimum excludant) of an array of integers is defined as the smallest non-negative integer which does not occur in the array. For example:

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  • The MEX of $[2,2,1]$ is $0$, because $0$ does not belong to the array.
  • The MEX of $[3,1,0,1]$ is $2$, because $0$ and $1$ belong to the array, but $2$ does not.
  • The MEX of $[0,3,1,2]$ is $4$, because $0$, $1$, $2$ and $3$ belong to the array, but $4$ does not.
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Input

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Each test contains multiple test cases. The first line contains a single integer $t$ ($1 \leq t \leq 2 \cdot 10^4$) — the number of test cases. The description of the test cases follows.

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The first line of each test case contains a single integer $n$ ($1 \le n \le 2 \cdot 10^5$).

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The second line of each test case contains $n$ integers $a_1, a_2, \ldots, a_n$ ($0 \le a_i \lt n$).

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It is guaranteed that the sum of $n$ over all test cases does not exceed $2 \cdot 10^5$.

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Output

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For each test case, find game's score if both players play optimally.

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Note

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In the first test case, a possible game with a score of $2$ is as follows:

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  1. Alice chooses the element $1$. After this move, $a=[0,0,1]$ and $c=[1]$.
  2. Bob chooses the element $0$. After this move, $a=[0,1]$ and $c=[1]$.
  3. Alice chooses the element $0$. After this move, $a=[1]$ and $c=[1,0]$.
  4. Bob chooses the element $1$. After this move, $a=[\,]$ and $c=[1,0]$.
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At the end, $c=[1,0]$, which has a MEX of $2$. Note that this is an example game and does not necessarily represent the optimal strategy for both players.

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样例

Input #1
3
4
0 0 1 1
4
0 1 2 3
2
1 1
Output #1
2
1
0
InputCopy OutputCopy
题目信息
题号
1944C
时间限制
2 s
内存限制
256 MB

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