Help me in solving REMOVEADD problem

help
,
1

My issue

not able solve this problem output is getting coorect but hidden test cases are failing

My code

#include <bits/stdc++.h>
using namespace std;

#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL);

void solve() {
    int n;
    cin >> n;
    vector<int> a(n);
    unordered_set<int> seen;
    int duplicates = 0;

    // Read the array and track duplicates
    for (int i = 0; i < n; i++) {
        cin >> a[i];
        if (seen.count(a[i]) > 0) {
            duplicates++;  // Count duplicates
        } else {
            seen.insert(a[i]); // Mark the element as seen
        }
    }

    // The number of operations required is equal to the number of duplicates
    cout << duplicates << '\n'; // Output the number of operations needed
}

int main() {
    fastio
    int T;
    cin >> T; // Number of test cases
    while (T--) {
        solve(); // Process each test case
    }
    return 0;
}

Problem Link: Remove and Add Practice Coding Problem