982 Div 2C

#include <bits/stdc++.h>
using namespace std;
mt19937_64 RNG(chrono::steady_clock::now().time_since_epoch().count());
#define NeedForSpeed                  \
    ios_base::sync_with_stdio(false); \
    cin.tie(NULL);                    \
    cout.tie(NULL);
#define int long long
#define all(x) (x).begin(), (x).end()
typedef vector<int> vi;
typedef vector<bool> vb;
typedef vector<vi> vvi;
typedef vector<pair<int, int>> vpi;
#define f first
#define s second
#define endl "\n"
const int mod = 1000000007;
int n;
vi v;
map<int, set<int>> adj;
set<int> visited;
int maxi = 0;
void dfs(int node)
{
    maxi = max(maxi, node);
    visited.insert(node);
    if (adj.count(node))
    {
        for (auto &i : adj[node])
        {
            if (!visited.count(i))
            {
                dfs(i);
            }
        }
    }
}
void solve()
{
    cin >> n;
    v.resize(n);
    adj.clear();
    visited.clear();
    for (int i = 0; i < n; i++)
    {
        cin >> v[i];
        int temp1 = v[i] + i;
        int temp2 = temp1 + i;
        if (i > 0)
        {
            adj[temp1].insert(temp2);
        }
    }
    maxi = 0;
    dfs(n);
    cout << maxi << endl;
}

signed main()
{
    NeedForSpeed;
    int t;
    cin >> t;
    while (t--)
    {
        solve();
    }
    return 0;
}