Bubble Sort Graph

The title means that you can find the longest ascending subsequence

#include"bits/stdc++.h"
#define ll long long
#define pi pair<int,int>
#define inf 0x3f3f3f3f
#define  _for(i,a,b) for(int i=a;i<=b;i++)
#define  for_(i,a,b) for(int i=a;i<b;i++)
#define _fr(i,a,b) for(int i=a;i>=b;i--)
#define fr_(i,a,b) for(int i=a;i>b;i--)
#define IOS ios::sync_with_stdio(false),cin.tie(0),cout.tie(0)
using namespace std;
const int N = 1e5+5;
const ll mod = 1e9+7;
const double lp=1.000000011;
map<char,int>mp;
int n,x;
int a[N],b[N],c[N];
void solve(){
    cin >> n;
    _for(i,1,n) cin >> a[i];
    _for(i,1,n) b[i]=inf;
    _for(i,1,n){
        int k = lower_bound(b+1,b+1+n,a[i])-b;
        c[i]=k;
        b[k]=a[i];
    }
    int ans = -inf;
    _for(i,1,n){
        ans = max(ans,c[i]);
    }
    cout << ans << endl;

}

int main()
{
    IOS;
    solve();
    return 0;
}