题目描述
Problem Description
In this country, there are $n$ cities initially connected by several bidirectional roads, resulting in $t \ge 2$ connected components. Specifically, the absolute difference in sizes between any two of these connected components does not exceed $0 \le k \le 1$. For the convenience of urban construction and development, $t$ cities among the $n$ cities have built at least one additional bidirectional road among these $t$ cities to make all cities connected.
Given all the roads after the additional construction, you need to calculate which sets of bidirectional roads $E'$ could be the ones that were later added. Please output the result modulo $998,244,353$.
That is, given an undirected connected graph $G = (V, E)$ with $n$ vertices and $m$ edges, you are asked to determine how many subgraphs $G' = (V', E')$ of this graph exist, such that $E' \ne \varnothing$ and $G - E'$ has exactly $|V'|$ connected components, with the absolute difference in sizes between any two components not exceeding $k$, where $0 \le k \le 1$. Please output the result modulo $998,244,353$.
Input Format
The first line of input contains three positive integers $n, m, k$, representing the number of cities, the number of roads after construction, and the upper limit of the absolute difference in sizes between any two connected components, respectively.
The next $m$ lines each contain two positive integers $u, v$, indicating that there is a bidirectional road between city $u$ and city $v$, with $u \ne v$.
Output Format
Output a single number representing the result modulo $998,244,353$.
Sample Input and Output
Input Sample #1
4 4 1
1 2
2 3
1 3
3 4
Output Sample #1
2
Input Sample #2
See attached file cities/cities2.in
Output Sample #2
See attached file cities/cities2.ans
Input Sample #3
See attached file cities/cities3.in
Output Sample #3
See attached file cities/cities3.ans
Input Sample #4
See attached file cities/cities4.in
Output Sample #4
See attached file cities/cities4.ans
Notes/Hints
[Sample 1 Explanation]
There are two possible scenarios:
- Initially, there was only one road $(3, 4)$, resulting in three connected components: $\{1\}$, $\{2\}$, and $\{3, 4\}$. Later, cities $1, 2, 3$ decided to build additional roads $(1, 2)$, $(2, 3)$, and $(1, 3)$ among themselves to connect all cities.
- Initially, there were no roads, resulting in four connected components: $\{1\}$, $\{2\}$, $\{3\}$, and $\{4\}$. Later, cities $1, 2, 3, 4$ decided to build additional roads $(1, 2)$, $(2, 3)$, $(1, 3)$, and $(3, 4)$ among themselves to connect all cities.
[Data Range]
For all data, it is guaranteed that: $3 \le n \le 10^5$, $n - 1 \le m \le 2 \times 10^5$, $0 \le k \le 1$.
| Test Point | $n$ | $m$ | $k$ |
|---|---|---|---|
| 1, 2 | $\le 15$ | $\le 20$ | $= 0$ |
| 3 ~ 5 | $\le 20$ | $\le 50$ | $= 1$ |
| 6, 7 | $\le 200$ | $\le 300$ | $= 0$ |
| 8, 9 | $\le 2,000$ | $= n - 1$ | $= 1$ |
| 10, 11 | $\le 2,000$ | $\le 3,000$ | $= 0$ |
| 12, 13 | $\le 2,000$ | $\le 3,000$ | $= 1$ |
| 14, 15 | $\le 10^5$ | $= n - 1$ | $= 1$ |
| 16, 17 | $\le 10^5$ | $\le 2 \times 10^5$ | $= 0$ |
| 18 ~ 20 | $\le 10^5$ | $\le 2 \times 10^5$ | $= 1$ |
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分