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;
}

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