Good Bye 2021: 2022 is NEAR
G
Just Add an Edge
Codeforces
3500
原题
← FH →
翻译中…

You are given a directed acyclic graph with $n$ vertices and $m$ edges. For all edges $a \to b$ in the graph, $a \lt b$ holds.

翻译中…

You need to find the number of pairs of vertices $x$, $y$, such that $x \gt y$ and after adding the edge $x \to y$ to the graph, it has a Hamiltonian path.

翻译中…

Input

翻译中…

The first line of input contains one integer $t$ ($1 \leq t \leq 5$): the number of test cases.

翻译中…

The next lines contains the descriptions of the test cases.

翻译中…

In the first line you are given two integers $n$ and $m$ ($1 \leq n \leq 150\,000$, $0 \leq m \leq \min(150\,000, \frac{n(n-1)}{2})$): the number of vertices and edges in the graph.

翻译中…

Each of the next $m$ lines contains two integers $a$, $b$ ($1 \leq a \lt b \leq n$), specifying an edge $a \to b$ in the graph. No edge $a \to b$ appears more than once.

翻译中…

Output

翻译中…

For each test case, print one integer: the number of pairs of vertices $x$, $y$, $x \gt y$, such that after adding the edge $x \to y$ to the graph, it has a Hamiltonian path.

翻译中…

Note

翻译中…

In the first example, any edge $x \to y$ such that $x \gt y$ is valid, because there already is a path $1 \to 2 \to 3$.

翻译中…

In the second example only the edge $4 \to 1$ is valid. There is a path $3 \to 4 \to 1 \to 2$ if this edge is added.

翻译中…

In the third example you can add edges $2 \to 1$, $3 \to 1$, $4 \to 1$, $4 \to 2$.

翻译中…

样例

Input #1
3
3 2
1 2
2 3
4 3
1 2
3 4
1 4
4 4
1 3
1 4
2 3
3 4
Output #1
3
1
4
InputCopy OutputCopy
题目信息
题号
1616G
时间限制
1 s
内存限制
256 MB
标签
DFS 及类似
动态规划
图论

题面与样例版权归 Codeforces 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。