The 19th Zhejiang Provincial Collegiate Programming Contest F - Easy Fix(主席树)

F - Easy Fix
发现交换 l，r不会影响 1到l-1和r+1到 n
对l+1，r-1的影响只有正负一（用主席树计算一下改变的量，一共四种情况）
对l和r再算一下

//#pragma GCC optimize(2)
//#pragma GCC optimize(3,"Ofast","inline")
#include<bits/stdc++.h>
#define int long long
#define fi first
#define se second
#define pb push_back
#define pii pair<int,int>
#define yes cout<<"YES\n"
#define no cout<<"NO\n"
#define IOS ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
using namespace std;
const int inf=8e18;
const int maxn=2e5+100;
int a[maxn],c[maxn],p[maxn],b[maxn],d[maxn],pre[maxn];
int lowbit(int x)
{
	return x&(-x);
}
void update(int x,int val)
{
	while(x<maxn)
	{
		c[x]+=val;
		x+=lowbit(x);
	}
}
int ask(int x)
{
	int ans=0;
	while(x>0)
	{
		ans+=c[x];
		x-=lowbit(x);
	}
	return ans;
}
struct node
{
	int l,r;
	int sum;
	int op[5];
} t[maxn*32];
int cnt,root[maxn];
void update(int l,int r,int &x,int y,int num,vector<int>v)
{
	x=++cnt;
	t[x]=t[y];
	t[x].sum++;
	for(auto it:v) t[x].op[it]++;
	//t[x].op[type]++;
	if(l==r)return ;
	int mid=(l+r)>>1;
	if(num<=mid) update(l,mid,t[x].l,t[y].l,num,v);
	else update(mid+1,r,t[x].r,t[y].r,num,v);
}

int query(int l,int r,int x,int y,int num,int type)//查询<= num [type]的个数
{
	if(r<=num)return t[y].op[type]-t[x].op[type];
	int mid=(l+r)>>1;
	int ans=0;
	if(num>=l) ans+=query(l,mid,t[x].l,t[y].l,num,type);
	if(num>mid) ans+=query(mid+1,r,t[x].r,t[y].r,num,type);
	return ans;
}
int query(int l,int r,int x,int y,int num)//查询<= num的个数
{
	if(r<=num)return t[y].sum-t[x].sum;
	int mid=(l+r)>>1;
	int ans=0;
	if(num>=l) ans+=query(l,mid,t[x].l,t[y].l,num);
	if(num>mid) ans+=query(mid+1,r,t[x].r,t[y].r,num);
	return ans;
}
signed main()
{
	IOS
	int n,q;
	cin>>n;
	for(int i=1; i<=n; i++)
	{
		cin>>p[i];
	}
	//cout<<"A:";
	for(int i=1; i<=n; i++)
	{
		a[i]=ask(p[i]);
		update(p[i],1);
		//cout<<a[i]<<" ";
	}
	//cout<<"\n";
	//cout<<"B:";
	for(int i=1; i<=n; i++) update(p[i],-1);
	for(int i=n; i>=1; i--)
	{
		b[i]=ask(p[i]);
		update(p[i],1);
		d[i]=min(a[i],b[i]);
	}
	for(int i=1; i<=n; i++)
	{
		//cout<<b[i]<<" ";
		pre[i]=pre[i-1]+d[i];
	}
	//cout<<"\n";
	for(int i=1; i<=n; i++)
	{
		vector<int>v;
		if(a[i]<=b[i]) v.pb(1);
		if(a[i]-1>b[i]) v.pb(2);
		if(a[i]>=b[i]) v.pb(3);
		if(a[i]<b[i]-1) v.pb(4);
		update(1,(int)1e6,root[i],root[i-1],p[i],v);
	}
	cin>>q;
	while(q--)
	{
		int l,r;
		cin>>l>>r;
		if(l>r) swap(l,r);
		if(l==r)
		{
			cout<<pre[n]<<"\n";
			continue;
		}
		int ans=pre[n]-d[l]-d[r];
		if(p[l]<p[r])
		{
			int s2=query(1,1e6,root[l],root[r-1],p[r],2)-query(1,1e6,root[l],root[r-1],p[l],2);
			int s1=query(1,1e6,root[l],root[r-1],p[r],1)-query(1,1e6,root[l],root[r-1],p[l],1);
			ans+=s2-s1;
		}
		else
		{
			int s4=query(1,1e6,root[l],root[r-1],p[l],4)-query(1,1e6,root[l],root[r-1],p[r],4);
			int s3=query(1,1e6,root[l],root[r-1],p[l],3)-query(1,1e6,root[l],root[r-1],p[r],3);
			ans+=s4-s3;
		}
		int low_l=query(1,1e6,root[l],root[r],p[l]);
		int low_r=query(1,1e6,root[l-1],root[r-1],p[r]);
		ans+=min(a[l]+low_l,b[l]-low_l);
		ans+=min(a[r]-low_r,b[r]+low_r);
		cout<<ans<<"\n";
	}
}