func_code_string: #include <bits/stdc++.h>   using namespace std;   long long sum[400006] = {0};   long long Min[400006] = {0};   long long Max[400006] = {0};   void solve() {     long long n;     cin >> n;     long long k;     cin >> k;     vector<long long> v(n);     for (long long i = 0; i < n; i++) cin >> v[i];     for (long long i = 0; i <= 2 * k + 3; i++) Min[i] = Max[i] = sum[i] = 0;     for (long long i = 0; i < n / 2; i++) {       Max[max(v[i], v[n - i - 1])]++;       Min[min(v[i], v[n - i - 1])]++;       sum[v[i] + v[n - i - 1]]++;     }     for (long long i = 1; i <= k; i++) {       Min[i] += Min[i - 1];       Max[i] += Max[i - 1];     }     long long ans = 2000000000000000005;     long long c;     for (long long i = 2; i <= k + 1; i++) {       c = Min[i - 1];       if (c <= n / 2) ans = min(ans, c + 2 * ((n / 2) - c) - sum[i]);     }     for (long long i = k + 1; i <= 2 * k; i++) {       if (i - k - 1 >= 0) c = Max[i - k - 1];       if (c <= n / 2) ans = min(ans, c * 2 + (n / 2 - c) - sum[i]);     }     cout << ans <<   n ;   }   signed main() {     ios_base ::sync_with_stdio(0);     cin.tie(NULL);     cout.tie(NULL);     long long t;     cin >> t;     while (t--) {       solve();     }     return 0;   }   