What is wrong in this code ?

general
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Question - CodeChef: Practical coding for everyone

#include <bits/stdc++.h>
#define endl “\n”
#define ll long long int
using namespace std;
const ll M = 1000000007;

void solve()
{
ll i, j, k, n, a, b, m, c, l, r, mid, sum, f;
ll ans = 0;

cin >> n;
vector<ll> o, e;
for (i = 0; i < n; i++)
{

    cin >> a;
    if (i % 2 == 0)
    {
        o.push_back(a);
    }
    else
    {
        e.push_back(a);
    }
}

sort(o.begin(), o.end(), greater<ll>());
sort(e.begin(), e.end());

for (i = 1; i < o.size(); i++)
{
    o[i] += o[i - 1];
}

for (i = 0; i < e.size(); i++)
{
    ans += (e[i] * o[i]);
}

for (i = 0; i < min(o.size(), e.size()); i++)
{
    if (i > 0)
    {
        cout << (o[i] - o[i - 1]) << " " << e[i] << " ";
    }
    else
    {
        cout << o[i] << " " << e[i] << " ";
    }
}

if ((n > 1) && (n % 2 != 0))
{
    cout << (o[i] - o[i - 1])<<" ";
}

cout << endl;

cout << ans;

cout << endl;

}

int main()
{

#ifndef ONLINE_JUDGE
freopen(“input.txt”, “r”, stdin);
freopen(“output.txt”, “w”, stdout);
#endif
ios_base::sync_with_stdio(false);
cin.tie(NULL);

ll t;
cin >> t;

while (t--)
{
    solve();
}

return 0;

}