好像LCT+啟發式合併更快？

#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<cmath>
#include<iostream>
#include<algorithm>
#define maxn 200010
#define N 2000010

using namespace std;

struct yts
{
	int op,x,y;
}q[maxn];

int n,T,in[maxn],out[maxn],tot,num,cnt;
int root[maxn],lch[N],rch[N],size[N],g[maxn],f[maxn],dep[maxn];
int head[maxn],to[maxn],next[maxn];
char s[5];

void addedge(int x,int y)
{
	num++;to[num]=y;next[num]=head[x];head[x]=num;
}

int find(int x)
{
	if (f[x]==x) return x;
	else return f[x]=find(f[x]);
}

void modify(int &i,int l,int r,int x)
{
	if (!i) i=++cnt;
	if (l==r) {size[i]=1;return;}
	int mid=(l+r)/2;
	if (x<=mid) modify(lch[i],l,mid,x);
	if (mid<x) modify(rch[i],mid+1,r,x);
	size[i]=size[lch[i]]+size[rch[i]];
}

void dfs(int x)
{
	in[x]=++tot;modify(root[x],1,n,in[x]);
	for (int p=head[x];p;p=next[p])
		if (to[p]!=g[x])
		{
			g[to[p]]=x;dep[to[p]]=dep[x]+1;
			dfs(to[p]);
		}
	out[x]=tot;
}

int merge(int x,int y)
{
	if (!x) return y;
	if (!y) return x;
	size[x]+=size[y];
	lch[x]=merge(lch[x],lch[y]);
	rch[x]=merge(rch[x],rch[y]);
	return x;
}

int query(int &root,int l,int r,int L,int R)
{
	if (!root) return 0;
	if (L<=l && r<=R) return size[root];
	int mid=(l+r)/2,ans=0;
	if (L<=mid) ans+=query(lch[root],l,mid,L,R);
	if (mid<R) ans+=query(rch[root],mid+1,r,L,R);
	return ans;
}

int main()
{
	scanf("%d%d",&n,&T);
	for (int i=1;i<=T;i++)
	{
		int x,y;
		scanf("%s%d%d",s,&x,&y);
		if (s[0]=='A') addedge(x,y),addedge(y,x);
		if (s[0]=='A') q[i].op=0,q[i].x=x,q[i].y=y;
		if (s[0]=='Q') q[i].op=1,q[i].x=x,q[i].y=y;
	}
	for (int i=1;i<=n;i++) if (!g[i]) dfs(i);
	for (int i=1;i<=n;i++) f[i]=i;
	for (int i=1;i<=T;i++)
	{
		if (q[i].op==0)
		{
			int x=find(q[i].x),y=find(q[i].y);
			if (dep[x]>dep[y]) swap(x,y);
			root[x]=merge(root[x],root[y]);
			f[y]=x;
		}
		else
		{
			int x=q[i].x,y=q[i].y;
			if (dep[x]<dep[y]) swap(x,y);
			int z=find(x);
			long long num=query(root[z],1,n,in[x],out[x]);
			printf("%lld\n",((long long)size[root[z]]-num)*num);
		}
	}
	return 0;
}