BZOJ 1832 聚会

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#define N 501000
#define LOGN 20
#define inf 0x3f3f3f3f
using namespace std;
struct KSD
{
    int v,next;
}e[N<<1];
int head[N],cnt;
inline void add(int u,int v)
{
    cnt++;
    e[cnt].v=v;
    e[cnt].next=head[u];
    head[u]=cnt;
}
int n,m;
int fa[N][LOGN],deep[N];
void dfs(int x,int p)
{
    int i,v;
    deep[x]=deep[p]+1;
    for(i=head[x];i;i=e[i].next)
    {
        v=e[i].v;
        if(v==p)continue;
        fa[v][0]=x;
        dfs(v,x);
    }
    return ;
}
inline void array()
{
    int i,j;
    for(j=1;j<LOGN;j++)
        for(i=1;i<=n;i++)
            fa[i][j]=fa[fa[i][j-1]][j-1];
}
int lcansx,lcansy;
inline int getlca(int x,int y)
{
    if(deep[x]<deep[y])swap(x,y);
    int i,j,k;
    lcansx=lcansy=0;
    for(i=LOGN-1;i>=0;i--)
        if(deep[fa[x][i]]>=deep[y])x=fa[x][i],lcansx+=(1<<i);
    if(x==y)return x;
    for(i=LOGN-1;i>=0;i--)
        if(fa[x][i]!=fa[y][i])
            x=fa[x][i],y=fa[y][i],lcansy+=(1<<i);
    lcansy+=1,lcansx+=lcansy;
    return fa[x][0];
}
int main()
{
//    freopen("test.in","r",stdin);
    int i,ans,id;
    int a,b,c;
    scanf("%d%d",&n,&m);
    for(i=1;i<n;i++)
    {
        scanf("%d%d",&a,&b);
        add(a,b),add(b,a);
    }
    dfs(1,0);
    array();
    while(m--)
    {
        scanf("%d%d%d",&a,&b,&c);

        int lca=getlca(a,b),temp=lcansx+lcansy;
        getlca(lca,c);
        temp+=lcansx+lcansy;
        ans=temp,id=lca;

        lca=getlca(a,c),temp=lcansx+lcansy;
        getlca(lca,b);
        temp+=lcansx+lcansy;
        if(ans>temp)ans=temp,id=lca;

        lca=getlca(b,c),temp=lcansx+lcansy;
        getlca(lca,a);
        temp+=lcansx+lcansy;
        if(ans>temp)ans=temp,id=lca;

        printf("%d %d\n",id,ans);
    }
    return 0;
}