QOJ.ac

QOJ

Time Limit: 6.0 s Memory Limit: 512 MB Total points: 100 Hackable ✓

#10523. 最小生成樹

Statistics

所有邊排序

並查集尋找祖先

不同就合併

——最小生

——炸雞塊君

給定整數 $n, k$,求有多少種不同的 $n$ 個節點的無向連通圖滿足:

  • 圖中沒有自環,且任意兩個點之間至多有一條邊。
  • 所有邊的邊權為 $[1, k]$ 之間的整數。
  • 對於圖中的每條邊,都至少存在一棵最小生成樹包含該邊。

兩張圖不同當且僅當存在一對節點 $(u, v)$,使得一張圖中 $u, v$ 之間有邊而另一張沒有,或是兩圖中 $u, v$ 之間的邊權不同。

請計算滿足條件的圖的數量,對 $998244353$ 取模。

輸入格式

每個測試文件僅有一組測試數據。

第一行包含兩個正整數 $n$ 和 $k$ ($1 \le n \le 5 \times 10^4, 1 \le k \le 10$)。

輸出格式

一行一個整數,表示答案對 $998244353$ 取模的結果。

範例

輸入 1

3 1

輸出 1

4

輸入 2

4 2

輸出 2

377

輸入 3

235 7

輸出 3

928998036

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