Jumpy Humpy - HackerEarth (Dynamic Programming , Stacks )

#include <bits/stdc++.h>
#define ll long long
using namespace std;
int main()
{
    ll n;
    cin >> n;
    vector<ll>arr(n, 0);
    for(int i = 0; i < n; i++)cin >> arr[i];
    vector<ll>nxt(n, 0);
    stack<ll>s;
    s.push(0);
    for(int i = 1; i < n; i++){
        while(!s.empty() && arr[i] > arr[s.top()]){
            nxt[s.top()] = i;
            s.pop();
        }
        s.push(i);
    }
    while(!s.empty()){
        nxt[s.top()] = -1;
        s.pop();
    }
    vector<ll>dp(n, 0);
    ll ans = 0;
    for(int i = n - 1; i >= 0; i--){
        if(nxt[i] == -1){
            dp[i] = arr[i];
            ans = max(ans, dp[i]);
            continue;
        }
        dp[i] = arr[i] ^ dp[nxt[i]];
        ans = max(ans, dp[i]);
    }
    cout << ans << endl;
    return 0;
}