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No.2345 max(l,r)

レベル : / AI推定難易度 : 2225 / 実行時間制限 : 1ケース 2.000秒 / メモリ制限 : 512 MB / 標準ジャッジ問題
タグ : (解説公開後に AC するまで非表示) / 解いたユーザー数 31
作問者 : ytqm3 / テスター : ぷら shiomusubi496
お気に入りにしたユーザー ProblemId : 9500 / 自分の提出
問題文最終更新日: 2023-06-09 13:44:18
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yukicoder contest 392 (順位表) の他の問題:

Problem Statement

Solve the following problem for $T$ cases.

Find the number, modulo $998244353$, of ways to place $N$ people on a number line such that the following conditions are satisfied.

  • The coordinate of every person is an integer between $1$ and $M$, inclusive.
  • For every $i\ (1 \le i \le N)$, let $l$ be the number of people at coordinates smaller than that of person $i$, and let $r$ be the number of people at coordinates larger than that of person $i$; then $\max(l,r)=A_i$.

Here, $2$ placements are considered different if and only if there exists a person $i$ such that the coordinate of person $i$ differs between them.

Input

$T$
$\text{case}_1$
$\text{case}_2$
$\vdots$
$\text{case}_T$

Each case is given in the following format.

$N$ $M$
$A_1$ $A_2$ $\ldots$ $A_N$
  • $1 \le T \le 2 \times 10^5$
  • $1 \le N,M \le 2 \times 10^5$
  • $0 \le A_i \le N-1$
  • The sum of $N$ over all cases does not exceed $2\times 10^5$.
  • All input values are integers.

Output

Print $T$ lines. On the $i$-th line, print the answer for $\text{case}_i$.

Sample

Sample 1
Input
3
5 5
4 3 2 3 4
1 5
0
7 7
1 1 1 1 6 1 1
Output
4
5
42

For the $1$st case: the following $4$ placements are possible.

  • Place person $1$ at coordinate $1$, person $2$ at coordinate $2$, person $3$ at coordinate $3$, person $4$ at coordinate $4$, and person $5$ at coordinate $5$.
  • Place person $1$ at coordinate $1$, person $2$ at coordinate $4$, person $3$ at coordinate $3$, person $4$ at coordinate $2$, and person $5$ at coordinate $5$.
  • Place person $1$ at coordinate $5$, person $2$ at coordinate $2$, person $3$ at coordinate $3$, person $4$ at coordinate $4$, and person $5$ at coordinate $1$.
  • Place person $1$ at coordinate $5$, person $2$ at coordinate $4$, person $3$ at coordinate $3$, person $4$ at coordinate $2$, and person $5$ at coordinate $1$.

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