bzoj1787 [Ahoi2008]Meet 紧急集合

#include<cstdio>
#include<iostream>
using namespace std;
#define LL long long
#define N 1000010
inline LL read()
{
    LL x=0,f=1;char ch=getchar();
    while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
    while(ch>=‘0‘&&ch<=‘9‘){x=x*10+ch-‘0‘;ch=getchar();}
    return x*f;
}
struct edge{
	int to,next;
}e[2*N];
int head[N];
int depth[N];
int go[N][25];
bool mrk[N];
int n,m,cnt,x,y,z,xy,xz,yz,sum;
inline int abs(int a)
{return a<0?-a:a;}
inline void ins(int u,int v)
{
	e[++cnt].to=v;
	e[cnt].next=head[u];
	head[u]=cnt;
}
inline void insert(int u,int v)
{
	ins(u,v);
	ins(v,u);
}
inline void dfs(int x,int dep)
{
	if (mrk[x])return;
	mrk[x]=1;depth[x]=dep;
	for (int i=1;i<=20;i++) go[x][i]=go[go[x][i-1]][i-1];
	for (int i=head[x];i;i=e[i].next)
	  if (!mrk[e[i].to])
	  {
	  	go[e[i].to][0]=x;
	  	dfs(e[i].to,dep+1);
	  }
} 
inline int lca(int x,int y)
{
	if (depth[x]<depth[y])swap(x,y);
	int res=depth[x]-depth[y];
	for(int i=0;i<=19;i++)
	  if (res & (1<<i)) x=go[x][i];
	for (int i=19;i>=0;i--)
	  if (go[x][i]!=go[y][i])
	  {
	  	x=go[x][i];
	  	y=go[y][i];
	  }
	if (x==y)return x;
	return go[x][0];
}
inline int dis(int a,int b)
{
	int t=lca(a,b);
	return depth[a]+depth[b]-2*depth[t];
}
inline int calc()
{
	xy=lca(x,y); xz=lca(x,z); yz=lca(y,z);
	int t;
	if (xy==xz)t=yz;
	if (xy==yz)t=xz;
	if (xz==yz)t=xy;
	int ans=dis(x,t)+dis(y,t)+dis(z,t);
	printf("%d %d\n",t,ans);
}
int main()
{
	n=read();m=read();
	for (int i=1;i<n;i++)
	{
		int s=read(),t=read();
		insert(s,t);
	}
	for(int i=0;i<20;i++)go[n/2][i]=n/2;
	dfs(n/2,1);
	for(int i=1;i<=m;i++)
	{
		x=read();
		y=read();
		z=read();
		calc();
	}
}