P4344 [SHOI2015]脑洞治疗仪

题目链接：

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define re register
#define pb push_back
#define fi first
#define se second
void read(int &a)
{
    a=0;int d=1;char ch;
    while(ch=getchar(),ch>'9'||ch<'0')
        if(ch=='-')
            d=-1;
    a=ch^48;
    while(ch=getchar(),ch>='0'&&ch<='9')
        a=(a<<3)+(a<<1)+(ch^48);
    a*=d;
}
struct note
{
    int l,r;
    mutable int v;
    note(int L,int R=-1,int V=0){l=L,r=R,v=V;}
    bool operator < (const note &x) const
    {
        return l<x.l;
    }
};
set <note> s;
set <note> :: iterator split(int pos)
{
    auto it=s.lower_bound(note(pos));
    if(it!=s.end()&&it->l==pos) return it;
    it--;
    if(it->r<pos) return s.end();
    int L=it->l,R=it->r,V=it->v;
    s.erase(it);
    s.insert(note(L,pos-1,V));
    return s.insert(note(pos,R,V)).fi;
}
void modify(int l,int r,int w)
{
    auto it2=split(r+1),it1=split(l);
    s.erase(it1,it2);
    s.insert(note(l,r,w));
}
void change(int l,int r,int x,int y)
{
    int sum=0;
    auto it2=split(r+1),it1=split(l),it=it1;
    for(;it1!=it2;it1++) sum+=it1->v?it1->r-it1->l+1:0;
    s.erase(it,it2);
    s.insert(note(l,r,0));
    if(!sum) return;
    it2=split(y+1),it1=split(x);
    if(sum>=y-x+1)
    {
        s.erase(it1,it2);
        s.insert(note(x,y,1));
        return;
    }
    for(;it1!=it2;it1++)
    {
        if(!it1->v)
        {
            sum-=it1->r-it1->l+1;
            if(sum<0)
            {
                modify(it1->l,it1->r+sum,1);
                break;
            }
            else it1->v=1;
        }
    }
}
int ask(int l,int r)
{
    int sum=0,ans=0;
    auto it2=split(r+1),it1=split(l);
    for(;it1!=it2;it1++)
    {
        if(!it1->v) sum+=it1->r-it1->l+1;
        else ans=max(sum,ans),sum=0;
    }
    return max(ans,sum);
}
int main()
{
    int n,m;
    read(n),read(m);
    s.insert(note(1,n,1));
    s.insert(note(n+1,n+1,0));
    for(re int i=1,op,l,r,x,y;i<=m;i++)
    {
        read(op);
        if(op==0) read(l),read(r),modify(l,r,0);
        else if(op==1) read(l),read(r),read(x),read(y),change(l,r,x,y);
        else read(l),read(r),printf("%d\n",ask(l,r));
    }
    return 0;
}