Bessie has a connected, undirected graph G with N vertices labeled 1…N and M edges (2≤N≤102,N−1≤M≤N2+N2). G may contain self-loops (edges from nodes back to themselves), but no parallel edges (multiple edges connecting the same endpoints).
Let fG(a,b) be a boolean function that evaluates to true if there exists a path from vertex 1 to vertex a that traverses exactly b edges for each 1≤a≤N and 0≤b, and false otherwise. If an edge is traversed multiple times, it is included that many times in the count.
Elsie wants to copy Bessie. In particular, she wants to construct an undirected graph G′ such that fG′(a,b)=fG(a,b) for all a and b.
Your job is to count the number of distinct graphs G′ that Elsie may create, modulo 109+7. As with G, G′ may contain self-loops but no parallel edges (meaning that there are 2N2+N2 distinct graphs on N labeled vertices in total).
Each input contains T (1≤T≤1054) test cases that should be solved independently. It is guaranteed that the sum of N2 over all test cases does not exceed 105.
INPUT FORMAT (input arrives from the terminal / stdin):
The first line of the input contains T, the number of test cases.
The first line of each test case contains the integers N and M.
The next M lines of each test case each contain two integers x and y (1≤x≤y≤N), denoting that there exists an edge between x and y in G.
Consecutive test cases are separated by newlines for readability.
OUTPUT FORMAT (print output to the terminal / stdout):
For each test case, the number of distinct G′ modulo 109+7 on a new line.
SAMPLE INPUT:
1 5 4 1 2 2 3 1 4 3 5
SAMPLE OUTPUT:
3In the first test case, G′ could equal G or one of the two following graphs:
5 4 1 2 1 4 3 4 3 5
5 5 1 2 2 3 1 4 3 4 3 5
SAMPLE INPUT:
7 4 6 1 2 2 3 3 4 1 3 2 4 1 4 5 5 1 2 2 3 3 4 4 5 1 5 5 7 1 2 1 3 1 5 2 4 3 3 3 4 4 5 6 6 1 2 2 3 3 4 4 5 5 6 6 6 6 7 1 2 2 3 1 3 1 4 4 5 5 6 1 6 10 10 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 1 10 22 28 1 2 2 3 3 4 4 5 5 6 6 7 1 7 1 8 3 9 8 10 10 11 10 12 10 13 10 14 11 15 12 16 13 17 14 18 9 15 9 16 9 17 9 18 15 19 19 20 15 20 16 21 21 22 16 22
SAMPLE OUTPUT:
45 35 11 1 15 371842544 256838540These are some larger test cases. Make sure to output the answer modulo 109+7. Note that the answer for the second-to-last test case is 2^{45}\pmod{10^9+7}.
SCORING:
- All test cases in input 3 satisfy N\le 5.
- All test cases in inputs 4-5 satisfy M=N-1.
- For all test cases in inputs 6-11, if it is not the case that f_G(x,b)=f_G(y,b) for all b, then there exists b such that f_G(x,b) is true and f_G(y,b) is false.
- Test cases in inputs 12-20 satisfy no additional constraints.
Problem credits: Benjamin Qi