BUPT 257

http://code.bupt.edu.cn/problem/p/257/

最近公共祖先LCA的离线Tarjan模板

#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
#include <algorithm>
#include <set>
#include <map>
#include <list>
#include <queue>
#include <stack>
#include <deque>
#include <vector>
#include <bitset>
#include <cmath>
#include <utility>
#define Maxn 100005
#define Maxm 1000005
#define lowbit(x) x&(-x)
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
#define PI acos(-1.0)
#define make_pair MP
#define LL long long
#define Inf (1LL<<62)
#define inf 0x3f3f3f3f
#define re freopen("in.txt","r",stdin)
#define wr freopen("out.txt","w",stdout)
using namespace std;
int p[Maxn];
int head[Maxn];
int qhead[Maxn];
int ancestor[Maxn];
int ans[Maxn];
int k,kk;
bool vis[Maxn];
int find(int x)
{
    return p[x]==-1?x:p[x]=find(p[x]);
}
void _union(int u,int v)
{
    int t1=find(u);
    int t2=find(v);
    if(t1!=t2)
        p[t2]=t1;
}
struct Edge
{
    int to;
    int next;
}edge[Maxm];
void addedge(int u,int v)
{
    edge[k].to=v;
    edge[k].next=head[u];
    head[u]=k++;
}
struct Query
{
    int q,next;
    int index;
}query[Maxn];
void add_query(int u,int v,int index)
{
    query[kk].q=v;
    query[kk].next=qhead[u];
    query[kk].index=index;
    qhead[u]=kk++;
    query[kk].q=u;
    query[kk].next=qhead[v];
    query[kk].index=index;
    qhead[v]=kk++;
}
void init()
{
    k=kk=0;
    memset(head,-1,sizeof(head));
    memset(qhead,-1,sizeof(qhead));
    memset(p,-1,sizeof(p));
    memset(ancestor,0,sizeof(ancestor));
    memset(vis,false,sizeof(vis));
}
void LCA(int u)
{
    ancestor[u]=u;
    vis[u]=true;
    for(int i=head[u];i!=-1;i=edge[i].next)
    {
        int v=edge[i].to;
        if(vis[v])
            continue;
        LCA(v);
        _union(u,v);
        ancestor[find(u)]=u;
    }
    for(int i=qhead[u];i!=-1;i=query[i].next)
    {
        int v=query[i].q;
        if(vis[v])
            ans[query[i].index]=ancestor[find(v)];
    }
}
int main()
{
    //re;
    //wr;
    int T,u,v,m,n;
    scanf("%d",&T);
    while(T--)
    {
        init();
        scanf("%d",&n);
        for(int i=1;i<n;i++)
        {
            scanf("%d %d",&u,&v);
            addedge(u,v);
        }
        scanf("%d",&m);
        for(int i=0;i<m;i++)
        {
            scanf("%d %d",&u,&v);
            add_query(u,v,i);
        }
        LCA(1);
        for(int i=0;i<m;i++)
            printf("%d\n",ans[i]);
    }
    return 0;
}