#include<algorithm>
#include<iostream>
const int N=1e3+10;
const int INF=0x3f3f3f3f;
using namespace std;
int n,t,a[N],b[N],c[N],d[N],e,m=-1;
int main()
{
	cin>>n;
	for(int i=1;i<=n;i=i+1){
		cin>>a[i];
	}
	for(int i=1;i<=n;i=i+1)
	{
		b[i]=1;
		for(int j=1;j<i;j=j+1)
		{
			if((a[i]>a[j])&&(b[i]<(b[j]+1)))
			{
				b[i]=b[j]+1;
			}
		}
	}
	for(int i=n;i>=1;i=i-1)
	{
		c[i]=1;
		e=0;
		for(int j=i+1;j<=n;j=j+1)
		{
			if((a[i]>a[j])&&(c[i]<(c[j]+1)))
			{
				c[i]=c[j]+1;
			}
		}
		m=max(b[i]+c[i],m);
	}
	cout<<m-1;
	return 0;
}

#include<cstdio>
#include<algorithm>
#include<iostream>
using namespace std;
int n,t,a[1005],b[1005],c[1005],bj[1005],bj2,m=-1;
int main()
{
	scanf("%d",&n);
	for(int i=1;i<=n;i=i+1)scanf("%d",&a[i]);
	for(int i=1;i<=n;i=i+1)
	{
		b[i]=1;
		for(int j=1;j<i;j=j+1)
		{
			if((a[i]>a[j])&&(b[i]<(b[j]+1)))
			{
				b[i]=b[j]+1;
			}
		}
	}
	for(int i=n;i>=1;i=i-1)
	{
		c[i]=1;
		bj2=0;
		for(int j=i+1;j<=n;j=j+1)
		{
			if((a[i]>a[j])&&(c[i]<(c[j]+1)))
			{
				c[i]=c[j]+1;
			}
		}
		m=max(b[i]+c[i],m);
	}
	printf("%d\n",m-1);
	return 0;
}

#include <bits/stdc++.h>
#define endl '\n'
using namespace std;
const int N=7e4,INF=0x3f3f3f3f,ANS=65535;
const int dx[]={1,-1,0,0},dy[]={0,0,1,-1};
typedef long long LL;
int n,ans;
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);cout.tie(nullptr);
	cin>>n;
	vector<int>a(n+1),dp1(n+1),dp2(n+1);
	for(int i=1;i<=n;i++){
		cin>>a[i];
		dp1[i] = dp2[i] = 1;
	}
	for(int i=1;i<=n;i++)for(int j=1;j<i;j++)if(a[i]>a[j])dp1[i] = max(dp1[i],dp1[j]+1);
	for(int i=n;i>=1;i--)for(int j=n;j>i;j--)if(a[i]>a[j])dp2[i] = max(dp2[i],dp2[j]+1);
	for(int i=1;i<=n;i++)ans = max(ans,dp1[i]+dp2[i]);
	cout<<ans-1;
	return 0;
}

#include<bits/stdc++.h>
using namespace std;
const int N=1005;
int a[N],dp[N],maxn=-114514,n;
int main(){
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>a[i];
		
	}
	for(int i=1;i<=n;i++){
		dp[i]=1;
		for(int j=1;j<i;j++){
			if(a[j]<a[i]){
				dp[i]=max(dp[i],dp[j]+1);
			}
			maxn=max(maxn,dp[i]);
		}
		
	}
	for(int i=1;i<=n;i++){
		
		for(int j=1;j<i;j++){
			if(a[j]>a[i]){
				dp[i]=max(dp[i],dp[j]+1);
			}
		}
		maxn=max(maxn,dp[i]);
	}
	cout<<maxn;
}

/****************************************
Note:
****************************************/
#include <queue>
#include <math.h>
#include <stack>
#include <vector>
#include <stdio.h>
#include <iostream>
#include <vector>
#include <iomanip>
#include <string.h>
#include <cstring>
#include <algorithm>
#define int long long
using namespace std;
const int N = 1e6 + 10;
const int INF = 0x3f3f3f3f;
int n;
int a[1005];
int dp[1005];
int maxn = -1;
signed main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	cin >> n;
	for(int i=1;i<=n;i++)
		cin >> a[i];
	for(int i=1;i<=n;i++){
		dp[i] = 1;
		for(int j=1;j<i;j++)
			if(a[j]<a[i])
				dp[i] = max(dp[i],dp[j] + 1);
		maxn = max(maxn,dp[i]);
	}
	for(int i=1;i<=n;i++){
		for(int j=1;j<i;j++)
			if(a[j]>a[i])
				dp[i] = max(dp[i],dp[j] + 1);
		maxn = max(maxn,dp[i]);
	}
	cout << maxn << endl;
	return 0;
}

合唱队形，模板中的模板

#include<iostream>
#include<cstring>
#define h using
#define uh namespace
#define e std
h uh e;
struct node{
	int x,up,down;
}a[1005];
int n,maxx;
int main(){
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>a[i].x;
		a[i].up=1,a[i].down=1;
	}
	for(int i=1;i<=n;i++)
		for(int j=1;j<i;j++)
			if(a[i].x>a[j].x)
				a[i].up=max(a[i].up,a[j].up+1);
	for(int i=n-1;i>=1;i--)
		for(int j=n;j>i;j--)
			if(a[i].x>a[j].x)
				a[i].down=max(a[i].down,a[j].down+1);
	for(int i=1;i<=n;i++){
		maxx=max(maxx,a[i].up+a[i].down-1);
	}
	cout<<maxx<<endl;
}
//       nb          AC