AwA，改了18个小时了，含注释和调试语句，共161行，下面放没有调试的代码，共132行：

#include<bits/stdc++.h>
#define ll long long
#define lson(x) x<<1
#define rson(x) x<<1|1
using namespace std;
const ll N=1e5+9;
struct node
{
	ll num1,num0;
	ll left1,left0,right1,right0;
	ll mid1,mid0;
	ll lazy_f,lazy_q,lt,rt,len; //lazy_f 赋值标记(-1)  lazy_q 取反标记(0)
}tr[N*4];
ll n,m,a[N];
inline node merge(node x,node y)
{
	return node({
		x.num1+y.num1,
		x.num0+y.num0,
		(x.num0?x.left1:x.num1+y.left1),
		(x.num1?x.left0:x.num0+y.left0),
		(y.num0?y.left1:y.num1+x.left1),
		(y.num1?y.left0:y.num0+x.left0),
		max(max(x.mid1,y.mid1),x.right1+y.left1),
		max(max(x.mid0,y.mid0),x.right0+y.left0)
	});
}
inline void put_down(ll id,ll type)
{
	if(type<=2)
	{
		if(type==1)
			tr[id]=node({0,tr[id].len,0,tr[id].len,0,tr[id].len,0,tr[id].len,0,0,tr[id].lt,tr[id].rt,tr[id].len});
		else
		{
			node x={tr[id].len,0,tr[id].len,0,tr[id].len,0,tr[id].len,0,1,0,tr[id].lt,tr[id].rt,tr[id].len};
			tr[id]=x;
		}
	}
	if(type==3)
		tr[id].lazy_q^=1,swap(tr[id].num0,tr[id].num1),
		swap(tr[id].left0,tr[id].left1),swap(tr[id].right0,tr[id].right1),
		swap(tr[id].mid0,tr[id].mid1);
}
inline void build(ll l,ll r,ll id)
{
	tr[id].len=r-l+1;
	tr[id].lt=l;
	tr[id].rt=r;
	tr[id].lazy_f=-1;
	if(l==r)
	{
		if(a[l]==1)
			tr[id].num1=tr[id].left1=tr[id].right1=tr[id].mid1=1;
		else 
			tr[id].num0=tr[id].left0=tr[id].right0=tr[id].mid0=1;
		return void();
	}
	ll mid=(l+r)>>1;
	build(l,mid,lson(id));
	build(mid+1,r,rson(id));
	tr[id].num1=tr[lson(id)].num1+tr[rson(id)].num1;
	tr[id].num0=tr[lson(id)].num0+tr[rson(id)].num0;
	tr[id].left1=(tr[lson(id)].num0?tr[lson(id)].left1:tr[lson(id)].num1+tr[rson(id)].left1);
	tr[id].left0=(tr[lson(id)].num1?tr[lson(id)].left0:tr[lson(id)].num0+tr[rson(id)].left0);
	tr[id].right1=(tr[rson(id)].num0?tr[rson(id)].right1:tr[rson(id)].num1+tr[lson(id)].right1);
	tr[id].right0=(tr[rson(id)].num1?tr[rson(id)].right0:tr[rson(id)].num0+tr[lson(id)].right0);
	tr[id].mid1=max(max(tr[lson(id)].mid1,tr[rson(id)].mid1),tr[lson(id)].right1+tr[rson(id)].left1);
	tr[id].mid0=max(max(tr[lson(id)].mid0,tr[rson(id)].mid0),tr[lson(id)].right0+tr[rson(id)].left0);
}
inline void push_down(ll id)
{
	if(tr[id].lazy_f!=-1)
		put_down(lson(id),tr[id].lazy_f+1),
		put_down(rson(id),tr[id].lazy_f+1);
	if(tr[id].lazy_q)
		put_down(lson(id),3),
		put_down(rson(id),3);
	tr[id].lazy_f=-1;
	tr[id].lazy_q=0;
}
inline void change(ll l,ll r,ll id,ll tp)
{
	push_down(id);
	if(r<tr[id].lt || l>tr[id].rt)
		return void();
	if(l<=tr[id].lt && r>=tr[id].rt)
	{
		put_down(id,tp);
		return void();
	}
	change(l,r,lson(id),tp);
	change(l,r,rson(id),tp);
	tr[id].num1=tr[lson(id)].num1+tr[rson(id)].num1;
	tr[id].num0=tr[lson(id)].num0+tr[rson(id)].num0;
	tr[id].left1=(tr[lson(id)].num0?tr[lson(id)].left1:tr[lson(id)].num1+tr[rson(id)].left1);
	tr[id].left0=(tr[lson(id)].num1?tr[lson(id)].left0:tr[lson(id)].num0+tr[rson(id)].left0);
	tr[id].right1=(tr[rson(id)].num0?tr[rson(id)].right1:tr[rson(id)].num1+tr[lson(id)].right1);
	tr[id].right0=(tr[rson(id)].num1?tr[rson(id)].right0:tr[rson(id)].num0+tr[lson(id)].right0);
	tr[id].mid1=max(max(tr[lson(id)].mid1,tr[rson(id)].mid1),tr[lson(id)].right1+tr[rson(id)].left1);
	tr[id].mid0=max(max(tr[lson(id)].mid0,tr[rson(id)].mid0),tr[lson(id)].right0+tr[rson(id)].left0);
}
inline node query(ll l,ll r,ll id)
{
	push_down(id);
	if(r<tr[id].lt || l>tr[id].rt)
		return node({0,0,0,0,0,0,0,0,0,0,0,0,0});
	if(tr[id].lt>=l && tr[id].rt<=r)
		return tr[id];
	return merge(query(l,r,lson(id)),query(l,r,rson(id)));
}
int main()
{
	cin>>n>>m;
	for(int i=1;i<=n;i++)
		cin>>a[i];
	build(1,n,1);
	while(m--)
	{
		ll opt,l,r;
		cin>>opt>>l>>r;
		opt++;l++;r++;
		if(opt==4)
			cout<<query(l,r,1).num1<<endl;
		else if(opt==5)
		{
			node tmp=query(l,r,1);
			cout<<tmp.mid1<<endl;
		} else change(l,r,1,opt);
	}
	return 0;
}

代码太长，见谅