loj2092 「ZJOI2016」大森林

ref不是太懂……

#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdio>
using namespace std;
int n, m, tot, val[200005], fa[200005], idx[200005], num, lf[200005], cnt;
int ans[200005], ch[200005][2], sum[200005], rg[200005], opt, uu, vv, ww;
struct Node{
	int pos, idx, u, v;
	bool operator<(const Node &x)const{
		if(pos!=x.pos)	return pos<x.pos;
		return idx<x.idx;
	}
}nd[400005];
int getW(int x){
	return ch[fa[x]][1]==x;
}
void upd(int x){
	sum[x] = sum[ch[x][0]] + sum[ch[x][1]] + val[x];
}
bool isRoot(int x){
	return ch[fa[x]][0]!=x && ch[fa[x]][1]!=x;
}
void rotate(int x){
	int old=fa[x], oldf=fa[old], w=getW(x);
	if(!isRoot(old))	ch[oldf][ch[oldf][1]==old] = x;
	ch[old][w] = ch[x][w^1]; ch[x][w^1] = old;
	fa[ch[x][w^1]] = x; fa[ch[old][w]] = old; fa[x] = oldf;
	upd(old); upd(x);
}
void splay(int x){
	while(!isRoot(x)){
		int f=fa[x];
		if(!isRoot(f))	rotate(getW(f)==getW(x)?f:x);
		rotate(x);
	}
	upd(x);
}
int access(int x){
	int y=0;
	while(x){
		splay(x);
		ch[x][1] = y;
		upd(x);
		y = x;
		x = fa[x];
	}
	return y;
}
void cut(int x){
	access(x);
	splay(x);
	fa[ch[x][0]] = 0;
	ch[x][0] = 0;
	upd(x);
}
int main(){
	cin>>n>>m;
	val[1] = lf[1] = tot = num = idx[1] = 1;
	rg[1] = n;
	fa[++tot] = 1;
	int now=tot;
	for(int i=1; i<=m; i++){
		scanf("%d", &opt);
		if(!opt){
			scanf("%d %d", &uu, &vv);
			val[++tot] = 1; idx[++num] = tot; lf[num] = uu; rg[num] = vv;
			fa[tot] = now;
		}
		else if(opt==1){
			scanf("%d %d %d", &uu, &vv, &ww);
			uu = max(uu, lf[ww]); vv = min(vv, rg[ww]);
			if(uu>vv)	continue;
			fa[++tot] = now;
			nd[++cnt] = (Node){uu, i-m, tot, idx[ww]};
			nd[++cnt] = (Node){vv+1, i-m, tot, now};
			now = tot;
		}
		else{
			scanf("%d %d %d", &ww, &uu, &vv);
			nd[++cnt] = (Node){ww, i, idx[uu], idx[vv]};
		}
	}
	sort(nd+1, nd+1+cnt);
	int k=1;
	memset(ans, -1, sizeof(ans));
	for(int i=1; i<=n; i++){
		for(; k<=cnt && nd[k].pos==i; k++){
			if(nd[k].idx<=0){
				cut(nd[k].u);
				fa[nd[k].u] = nd[k].v;
			}
			else{
				access(nd[k].u); splay(nd[k].u); int qwq=sum[nd[k].u];
				int t=access(nd[k].v); splay(nd[k].v); qwq += sum[nd[k].v];
				access(t); splay(t); qwq -= sum[t] << 1;
				ans[nd[k].idx] = qwq;
			}
		}
	}
	for(int i=1; i<=m; i++)
		if(ans[i]>=0)
			printf("%d\n", ans[i]);
	return 0;
}