聪聪可可

#include <iostream>
#include <cstdio>
using namespace std;
int read()
{
	int x=0,f=1;
	char c=getchar();
	while(c<'0'||c>'9')
	{
		if(c=='-')  f=-1;
		c=getchar();
	}
	while(c>='0'&&c<='9')
	{
		x=x*10+c-'0';
		c=getchar();
	}
	return f*x;
}
const int N=30000;
int root,size[N],sum,maxson[N],rem[N],num;
int had[N],to[N*2],len[N*2],nxt[N*2],p;
int n,a1,b1,c1,dis[N],x[3],y[3],ans,cnt,d;
bool f[N];
int gcd(int a,int b)
{
	if(!b)  return a;
	return gcd(b,a%b);
}
void add(int x,int y,int z)
{
	nxt[++p]=had[x];
	to[p]=y;
	len[p]=z;
	had[x]=p;
}
void getroot(int u,int fa)
{
	size[u]=1;  maxson[u]=0;
	for(int i=had[u];i;i=nxt[i])
	{
		int v=to[i];
		if(v==fa||f[v])  continue;
		getroot(v,u);
		size[u]+=size[v];
		maxson[u]=max(maxson[u],size[v]);
	}
	maxson[u]=max(maxson[u],sum-size[u]);
	if(maxson[u]<maxson[root])  root=u;
}
void getdis(int u,int fa)
{
	rem[++num]=dis[u]%3;
	for(int i=had[u];i;i=nxt[i])
	{
		int v=to[i];
		if(v==fa||f[v])  continue;
		dis[v]=dis[u]+len[i];
		getdis(v,u);
	}
}
void solve(int u)
{
	x[0]=1;  x[1]=x[2]=0;
	for(int i=had[u];i;i=nxt[i])
	{
		int v=to[i];
		if(f[v])  continue;
		y[0]=y[1]=y[2]=0;
		num=0;  dis[v]=len[i];
		getdis(v,u);
		for(int i=1;i<=num;i++)  y[rem[i]]++;
		ans+=(x[0]*y[0]+x[1]*y[2]+x[2]*y[1])*2;
		x[0]+=y[0];  x[1]+=y[1];  x[2]+=y[2];
	}
}
void divide(int u)
{
	f[u]=1;  solve(u);
	for(int i=had[u];i;i=nxt[i])
	{
		int v=to[i];
		if(f[v])  continue;
		sum=size[v];  root=0;
		getroot(v,0);  divide(root);
	}
}
int main()
{
	n=read();  cnt=n*n;  ans+=n;
	for(int i=1;i<n;i++)
	{
		a1=read();  b1=read();  c1=read();
		add(a1,b1,c1);  add(b1,a1,c1);
	}
	maxson[root]=sum=n;
	getroot(1,0);  divide(root);
	d=gcd(ans,cnt);
	cout<<ans/d<<"/"<<cnt/d;
	return 0;
}

标签：可可,std,&&,int,while,聪聪,include,getchar
来源： https://blog.csdn.net/qq_42192786/article/details/89920388