340D - Bubble Sort Graph - CodeForces Solution

#include <bits/stdc++.h>
using namespace std;
const int N=100010;
int a[N],f[N];
int n;

int main(){
    ios::sync_with_stdio(0),cin.tie(0);
    
    cin>>n;
    for(int i=1;i<=n;++i)cin>>a[i];
    int cnt=0;
    for(int i=1;i<=n;++i){
        if(f[cnt]<a[i])f[++cnt]=a[i];
        else f[lower_bound(f+1,f+1+cnt,a[i])-f]=a[i];
    }
    cout<<cnt;
    return 0;
}