
USACO 2024 December Contest, Platinum
Problem 3. Maximize Minimum Difference
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**Note: The time limit for this problem is 4s, twice the default.**
Moo! You are given an integer N (2≤N≤2000). Consider all permutations p=[p0,p1,…,pN−1] of [0,1,2…,N−1]. Let f(p)=min denote the minimum absolute difference between any two consecutive elements of p. and let S denote the set of all p that achieve the maximum possible value of f(p).
You are additionally given K (0\le K\le N) constraints of the form p_i=j (0\le i,j<N). Count the number of permutations in S satisfying all constraints, modulo 10^9+7.
INPUT FORMAT (input arrives from the terminal / stdin):
The first line contains T (1\le TN\le 2\cdot 10^4) and N, meaning that you will need to solve T independent test cases, each specified by a different set of constraints.Each test case starts with K, followed by K lines each containing i and j. It is guaranteed that
- The same i does not appear more than once within the same test case.
- The same j does not appear more than once within the same test case.
OUTPUT FORMAT (print output to the terminal / stdout):
For each test case, the answer modulo 10^9+7 on a separate line.SAMPLE INPUT:
3 4 0 1 1 1 2 0 2 2 3
SAMPLE OUTPUT:
2 0 1
The maximum possible value of f(p) is 2, and S=\{[2,0,3,1], [1,3,0,2]\}.
SAMPLE INPUT:
9 11 2 0 5 6 9 3 0 5 6 9 1 0 4 0 5 6 9 1 0 4 7 5 0 5 6 9 1 0 4 7 2 6 6 0 5 6 9 1 0 4 7 2 6 9 3 7 0 5 6 9 1 0 4 7 2 6 9 3 5 2 8 0 5 6 9 1 0 4 7 2 6 9 3 5 2 7 4 9 0 5 6 9 1 0 4 7 2 6 9 3 5 2 7 4 3 1 10 0 5 6 9 1 0 4 7 2 6 9 3 5 2 7 4 3 1 8 10
SAMPLE OUTPUT:
6 6 1 1 1 1 1 1 1
p=[5, 0, 6, 1, 7, 2, 9, 4, 10, 3, 8] should be counted for all test cases.
SAMPLE INPUT:
10 11 0 1 3 8 2 3 8 5 7 3 3 8 5 7 4 2 4 3 8 5 7 4 2 10 6 5 3 8 5 7 4 2 10 6 8 10 6 3 8 5 7 4 2 10 6 8 10 1 9 7 3 8 5 7 4 2 10 6 8 10 1 9 7 5 8 3 8 5 7 4 2 10 6 8 10 1 9 7 5 2 3 9 3 8 5 7 4 2 10 6 8 10 1 9 7 5 2 3 6 0
SAMPLE OUTPUT:
160 20 8 7 2 1 1 1 1 1
p=[4, 9, 3, 8, 2, 7, 0, 5, 10, 1, 6] should be counted for all test cases.
SAMPLE INPUT:
5 987 3 654 321 543 210 432 106 2 654 321 543 210 1 654 321 1 0 493 0
SAMPLE OUTPUT:
0 538184948 693625420 932738155 251798971
Make sure to output the answer modulo 10^9+7.
SCORING:
- Input 5: N=15
- Input 6: N=2000
- Inputs 7-9: For all test cases, the constraint p_0=\lfloor N/2\rfloor appears.
- Inputs 10-13: For all test cases, there exists some constraint p_i = j with j equal to \lfloor N/2\rfloor.
- Inputs 14-20: No additional constraints.
Problem credits: Benjamin Qi