//贪心
#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;

const int N = 100010;
int n;
vector<int> stk;
int arr[N];

int main()
{
    cin>>n;
    for (int i = 0; i < n; i ++ ) scanf("%d", &arr[i]);
    stk.push_back(arr[0]);
    for(int i=1;i<n;i++)
    {
        if(arr[i]>stk.back())
        {
            stk.push_back(arr[i]);
        }
        else
        {
            *lower_bound(stk.begin(),stk.end(),arr[i])=arr[i];
        }
    }
    cout<<stk.size();
    return 0;
}

回顾一下lower_bound()的用法，传进去三个参数

#include <iostream>
#include <cstring>
#include <algorithm>
#include <vector>


using namespace std;

const int N = 100010;
int arr[N];
vector<int> v;

int n;
int main()
{
    cin>>n;
    for(int i=1;i<=n;i++) scanf("%d", &arr[i]);
    v.push_back(arr[1]);
    for(int i=2;i<=n;i++)
    {
        if(arr[i]>v.back())
        {
            v.push_back(arr[i]);
        }
        else
        {
            *lower_bound(v.begin(),v.end(),arr[i])=arr[i];  
        }
    }
    cout<<v.size();

}