CF724F.Uniformly Branched Trees
省选/NOI-
通过率:0%
时间限制:1.00s
内存限制:256MB
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题目描述
A tree is a connected graph without cycles.
Two trees, consisting of n vertices each, are called isomorphic if there exists a permutation p: {1, ..., n} → {1, ..., n} such that the edge (u, v) is present in the first tree if and only if the edge (p__u, p__v) is present in the second tree.
Vertex of the tree is called internal if its degree is greater than or equal to two.
Count the number of different non-isomorphic trees, consisting of n vertices, such that the degree of each internal vertex is exactly d. Print the answer over the given prime modulo mod.
树是无环的连通图。
由 n 个顶点构成的两棵树被称为同构的,若存在一个置换 p:{1,…,n}→{1,…,n},使得边 (u,v) 在第一棵树中存在当且仅当边 (pu,pv) 在第二棵树中存在。
树的一个顶点称为内部顶点,当且仅当它的度数大于等于 2。
计算满足以下条件的互不同构的树的数目:该树恰含 n 个顶点,且每个内部顶点的度数恰好为 d。将答案对给定的素数模 mod 取模后输出。
输入格式
The single line of the input contains three integers n, d and mod (1 ≤ n ≤ 1000, 2 ≤ d ≤ 10, 108 ≤ mod ≤ 109) — the number of vertices in the tree, the degree of internal vertices and the prime modulo.
输入仅包含一行,三个整数 n、d 和 mod(1 ≤ n ≤ 1000,2 ≤ d ≤ 10,108 ≤ mod ≤ 109)—— 分别表示树的顶点数、内部顶点的度数以及模数(质数)。
输出格式
Print the number of trees over the modulo mod.
在模 mod 意义下输出树的个数。
输入输出样例
输入#1
5 2 433416647
输出#1
1
输入#2
10 3 409693891
输出#2
2
输入#3
65 4 177545087
输出#3
910726
输入解题思路,AI测评打分。不知道怎么写?