BZOJ4551 Tjoi2016&Heoi2016树（离线+并查集）

　　似乎是弱化的qtree3。树剖什么的非常无脑。考虑离线。并查集维护每个点的最近打标记祖先，倒序处理，删除标记时将其与父亲合并即可。

#include<iostream> 
#include<cstdio>
#include<cmath>
#include<cstdlib>
#include<cstring>
#include<algorithm>
#include<stack>
using namespace std;
int read()
{
    int x=0,f=1;char c=getchar();
    while (c<'0'||c>'9') {if (c=='-') f=-1;c=getchar();}
    while (c>='0'&&c<='9') x=(x<<1)+(x<<3)+(c^48),c=getchar();
    return x*f;
}
char getc(){char c=getchar();while ((c<'A'||c>'Z')&&(c<'a'||c>'z')) c=getchar();return c;}
#define N 100010
int n,m,p[N],cnt[N],fa[N],f[N],t;
bool flag[N];
stack<int> v;
struct data{int to,nxt;
}edge[N];
struct data2{int op,x;
}q[N];
void addedge(int x,int y){t++;edge[t].to=y,edge[t].nxt=p[x],p[x]=t;}
void dfs(int k,int from)
{
    if (cnt[k]) fa[k]=k;else fa[k]=from;
    for (int i=p[k];i;i=edge[i].nxt)
    if (edge[i].to!=from) f[edge[i].to]=k,dfs(edge[i].to,k);
}
int find(int x){return fa[x]==x?x:fa[x]=find(fa[x]);}
int main()
{
#ifndef ONLINE_JUDGE
    freopen("bzoj4551.in","r",stdin);
    freopen("bzoj4551.out","w",stdout);
    const char LL[]="%I64d\n";
#else
    const char LL[]="%lld\n";
#endif
    n=read(),m=read();
    for (int i=1;i<n;i++)
    {
        int x=read(),y=read();
        addedge(x,y);
    }
    for (int i=1;i<=m;i++) q[i].op=getc()=='C',q[i].x=read(),cnt[q[i].x]+=q[i].op;
    cnt[1]++;dfs(1,1);
    for (int i=m;i>=1;i--)
    if (q[i].op)
    {
        cnt[q[i].x]--;
        if (!cnt[q[i].x]) fa[q[i].x]=find(f[q[i].x]);
    }
    else v.push(find(q[i].x));
    while (!v.empty()) printf("%d\n",v.top()),v.pop();
    return 0;
}