Longest Increasing Subsequence

help
,
1

My code with out memozation:
#include<bits/stdc++.h>
#define F first;
#define S second;
#define PB push_back;
#define er erase;

#define MP make_pair;
#define fastio ios_base::sync_with_stdio(0);cin.tie(NULL);cout.tie(NULL);
const long long MOD = 1e9 + 7;
const long long INF = 1e9 + 7;
typedef long long int ll;
using namespace std;
ll arr[100001],n;
ll solve(ll i,ll prev,ll dp[])
{
    if(i==n)
    {
        return 0;
    }


    else
    {
        if(arr[i]>=prev)
        {
            return max(solve(i+1,prev=arr[i],dp)+1,solve(i+1,prev,dp));
        }
        else
        {
            return solve(i+1,prev,dp);


        }
    }
}



int main()
{

    fastio;
    ll prev=-INF;
    cin>>n;
    for(ll i=0;i<n;i++)
    {
        cin>>arr[i];
    }
    ll dp[n+1];
    memset(dp,-1,sizeof(dp));
    ll i=0;
    cout<<solve(i,prev,dp)<<endl;


    return 0;
}

How do i have to store the subproblem in array named dp?