[bzoj1787][Ahoi2008]紧急集合

#include<cmath>
#include<ctime>
#include<queue>
#include<stack>
#include<cstdio>
#include<vector>
#include<cstring>
#include<cstdlib>
#include<iostream>
#include<algorithm>
#define K 20
#define N 500005
using namespace std;
struct graph{
    int nxt,to;
}e[N<<1];
int f[N][K],g[N],dep[N],a,b,c,n,m,x,y,z,cnt;
stack<int> s;
inline int read(){
    int ret=0;char c=getchar();
    while(!isdigit(c))
        c=getchar();
    while(isdigit(c)){
        ret=(ret<<1)+(ret<<3)+c-‘0‘;
        c=getchar();
    }
    return ret;
}
inline void addedge(int x,int y){
    e[++cnt].nxt=g[x];g[x]=cnt;e[cnt].to=y;
}
inline void dfs(int u){
    dep[u]=1;s.push(u);
    while(!s.empty()){
        u=s.top();s.pop();
        if(u==1) for(int i=0;i<K;++i)
            f[u][i]=1;
        else for(int i=1;i<K;++i)
            f[u][i]=f[f[u][i-1]][i-1];
        for(int i=g[u];i;i=e[i].nxt)
            if(!dep[e[i].to]){
                dep[e[i].to]=dep[u]+1;
                f[e[i].to][0]=u;
                s.push(e[i].to);
            }
    }
}
inline int swim(int x,int h){
    for(int i=0;h;++i,h>>=1)
        if(h&1) x=f[x][i];
    return x;
}
inline int lca(int x,int y){
    if(dep[x]<dep[y]){
        int t=x;x=y;y=t;
    }
    x=swim(x,dep[x]-dep[y]);
    if(x==y) return x;
    int i;
    while(true){
        for(i=0;f[x][i]!=f[y][i];++i);
        if(!i) return f[x][0];
        x=f[x][i-1];y=f[y][i-1];
    }
} 
inline void init(){
    n=read();m=read();
    for(int i=1,j,k;i<n;++i){
        j=read();k=read();
        addedge(j,k);addedge(k,j);
    }
    dfs(1);
    while(m--){
        x=read();y=read();z=read();
        a=lca(x,y);b=lca(y,z);c=lca(x,z);
        if(a==b&&b==c)
            printf("%d %d\n",a,dep[x]+dep[y]+dep[z]-dep[a]*3);
        else if(a==b) printf("%d %d\n",c,dep[x]+dep[y]+dep[z]-dep[c]-(dep[a]<<1));
        else if(a==c) printf("%d %d\n",b,dep[x]+dep[y]+dep[z]-dep[b]-(dep[a]<<1));
        else printf("%d %d\n",a,dep[x]+dep[y]+dep[z]-dep[a]-(dep[b]<<1));
    }
}
int main(){
    freopen("meet.in","r",stdin);
    freopen("meet.out","w",stdout);
    init();
    fclose(stdin);
    fclose(stdout);
    return 0;
}