Help me in solving CREATEPERM problem

help
,
1

My issue

I followed this approach to solve the problem - CodeChef: Practical coding for everyone
Why is the test cases failing ?
Am I missing something ? Can someone please explain ?

My code

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

int main() {
    long long int test_cases;
    cin >> test_cases;
    while (test_cases--)
    {
        long long int n;
        cin >> n;
        
        if (n<=3)
        {
            for (long long int i=1; i<=n; i++)
                cout << i << " ";
            cout << endl;
            continue;
        }
        
        vector<long long int> ans(n);
        long long int x = ceil(n/2.0);
        
        long long int p = 0;
        long long int q = 1;
        
        for (long long int i=1; i<=x; i++)
        {
            ans[p] = i;
            p += 2;
        }
        for (long long int j=x+1; j<=n; j++)
        {
            ans[q] = j;
            q += 2;
        }
        
        for (long long int idx=0; idx<n; idx++)
        {
            cout << ans[idx] << " ";
        }
        cout << endl;
    }
}

Problem Link: Permutation Construction Practice Coding Problem