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其实，就是求n个点的生成树的个数。下面就是如果求生成树的个数： Matrix-Tree定理(Kirchhoff矩阵-树定理)。Matrix-Tree定理是解决生成树计数问题最有力的武器之一。它首先于1847年被Kirchhoff证明。在介绍定理之前，我们首先明确几个概念： 1、G的度数矩阵D[G]是一个n*n的矩阵，并且满足：当i≠j时,dij=0；当i=j时，dij等于vi的度数。 2、G的

#include<cstdio>#include<cmath>#include<cstring>#include<iostream>#include<algorithm>#include<queue>#include<string>using namespace std;#define INF 0x3f3f3f3ftypedef __int64 ll;struct node{

#include<cstdio>#include<cmath>#include<cstring>#include<iostream>#include<algorithm>#include<queue>#include<string>using namespace std;#define INF 0x3f3f3f3ftypedef __int64 ll;struct node{

#include<cstdio>#include<cmath>#include<cstring>#include<iostream>#include<algorithm>#include<queue>#include<string>using namespace std;#define INF 0x3f3f3f3ftypedef __int64 ll;int f[2505];i