HDU 4008 Parent and son

#include <stdio.h>
#include <algorithm>
#include <string.h>
#include <queue>
#include <stack>
#include <map>
#include <vector>
using namespace std;

const int maxn=100000+10;
const int INF=0x7fffffff;

int n,m;
vector<int>tree[maxn];
bool vis[maxn];
int MinSon[maxn],CiSon[maxn];
int MinDes[maxn],CiDes[maxn];
int belong[maxn];
int Fa;
int MinSonPos;
int MinDesPos;
int CiSonPos;
int CiDesPos;
struct P
{
    int a,b;
}pp[maxn];
bool cmp(const P&a,const P&b) { return a.b<b.b;}

int par[maxn];
int dfnIn[maxn],dfnOut[maxn];
int time;
int fa[maxn],l[maxn],p[maxn][25];
 int top, sun;
 struct Edge{
     int v;
     Edge* next;
 }*adj[maxn], edge[maxn << 1];

 void add(int u, int v){
      Edge* p = &edge[++top];
       p -> v = v;
       p -> next = adj[u];
       adj[u] = p;
 }
 void DFS(int u, int father, int depth){

      fa[u] = father;  l[u] = depth;
      for(Edge* p = adj[u]; p; p = p -> next){
            int v = p -> v;
            if(v == father) continue;

            DFS(v, u, depth + 1);

      }
 }
 void init_p(int n){
      int log = 0;
      for(; (1 << log) < n; log++); log--;
      for(int i = 1; i <= n; i++){
          for(int j = 0; j <= log; j++)  p[i][j] = -1;
      }
      for(int i = 1; i <= n; i++) p[i][0] = fa[i];
      for(int j = 1; j <= log; j++){
          for(int i = 1; i <= n; i++) if(p[i][j - 1] != -1) p[i][j] = p[p[i][j - 1]][j - 1];
      }
 }
 int query(int a, int b){
     int log, i;
     if(l[a] < l[b]) swap(a, b);
     for(log = 1; (1 << log) <= l[a]; log++); log--;
     for(i = log; i >= 0; i--){
         if(l[a] - (1 << i) > l[b]){
             a = p[a][i];
         }
     }
     sun = a;
     if(fa[a] == b) return b;
     a = fa[a];
     for(i = log; i >= 0; i--)
         if(p[a][i] != -1 && p[a][i] != p[b][i]){
             a = p[a][i]; b = p[b][i];
         }
     return fa[a];
 }

void init()
{
    top = 0;time=0;
    for(int i = 1; i <= n; i++) adj[i] = 0;
    memset(vis,0,sizeof vis);
    for(int i=1;i<=n;i++) MinSon[i]=INF,MinDes[i]=INF;
    for(int i=1;i<=n;i++) CiSon[i]=INF,CiDes[i]=INF;
    for(int i=1;i<=n;i++) tree[i].clear();
}

void read()
{
    for(int i=1; i<n; i++)
    {
        int u,v;
        scanf("%d%d",&u,&v);
        add(u,v);
        add(v,u);
        tree[u].push_back(v);
        tree[v].push_back(u);
    }
}

void dfs(int now)
{
    dfnIn[now]=++time;
    if(now!=1) belong[now]=Fa;

    bool fail=1;
    for(int i=0;i<tree[now].size();i++)
        if(!vis[tree[now][i]]) fail=0;

    if(fail)
    {
        dfnOut[now]=++time;
        return;
    }
    int *ff= new int[tree[now].size()+5];
    for(int i=0;i<tree[now].size();i++) ff[i]=0;
    for(int i=0;i<tree[now].size();i++)
    {
        if(vis[tree[now][i]]) continue;
        ff[i]=1; par[tree[now][i]]=now;
        if(now==1) Fa=tree[now][i];
        vis[tree[now][i]]=1;
        dfs(tree[now][i]);
        MinSon[now]=min(MinSon[now],tree[now][i]);
        MinDes[now]=min(MinDes[now],MinDes[tree[now][i]]);
    }
    MinDes[now]=min(MinDes[now],MinSon[now]);

    for(int i=0;i<tree[now].size();i++)
    {
        if(!ff[i]) continue;
        if(tree[now][i]!=MinSon[now])
            CiSon[now]=min(CiSon[now],tree[now][i]);

        if(MinDes[tree[now][i]]!=MinDes[now])
            CiDes[now]=min(CiDes[now],MinDes[tree[now][i]]);

        if(CiDes[tree[now][i]]!=MinDes[now])
            CiDes[now]=min(CiDes[now],CiDes[tree[now][i]]);

    }
    if(MinSon[now]!=MinDes[now])
        CiDes[now]=min(CiDes[now],MinSon[now]);

    dfnOut[now]=++time;

    delete []ff;
}

void work()
{
    memset(vis,0,sizeof vis);
    DFS(1, -1, 0);
    init_p(n);
    vis[1]=1;dfs(1);
    
    MinSonPos=INF; MinDesPos=INF;
    CiSonPos=INF; CiDesPos=INF;

    for(int i=0;i<tree[1].size();i++)
        MinSonPos=min(MinSonPos,tree[1][i]);

    for(int i=0;i<tree[1].size();i++)
    {
        if(tree[1][i]==MinSonPos) continue;
        CiSonPos=min(CiSonPos,tree[1][i]);
    }

    int yy=0;
    for(int i=0;i<tree[1].size();i++)
    {
        pp[yy].a=tree[1][i];
        pp[yy++].b=min(tree[1][i],MinDes[tree[1][i]]);
    }
    sort(pp,pp+yy,cmp);
    MinDesPos=pp[0].a;
    if(yy>=1) CiDesPos=pp[1].a;


    for(int i=1;i<=m;i++)
    {
        int X,Y;
        scanf("%d%d",&X,&Y);
        int U=query(X,Y);

        if(U!=Y)
        {
            if(MinDes[Y]==INF) printf("no answers!\n");
            else printf("%d %d\n",MinSon[Y],MinDes[Y]);
        }

        else
        {
            if(Y==1)
            {
                int ans1,ans2;
                int be=belong[X];
                if(MinSonPos==be) ans1=CiSonPos;
                else ans1=MinSonPos;
                if(MinDesPos==be) ans2=CiDesPos;
                else ans2=MinDesPos;
                if(ans1==INF||ans2==INF) printf("no answers!\n");
                else printf("%d %d\n",ans1,min(ans2,MinDes[ans2]));
            }
            else
            {
                int ans=INF;
                if(dfnIn[X]>=dfnIn[MinSon[Y]]&&dfnOut[X]<=dfnOut[MinSon[Y]]) ans=min(CiSon[Y],par[Y]);
                else if(dfnIn[MinSon[Y]]>=dfnIn[X]&&dfnOut[MinSon[Y]]<=dfnOut[X]) ans=min(CiSon[Y],par[Y]);
                else ans=min(MinSon[Y],par[Y]);
                printf("%d 1\n",ans);
            }
        }
    }
}

int main()
{
    int T;

    scanf("%d",&T);
    while(T--)
    {
        scanf("%d%d",&n,&m);
        init();
        read();
        work();
        printf("\n");
    }
    return 0;
}