#include <bits/stdc++.h>   using namespace std;   long long n, a[569], sq[250069], zs, inf = 1e18;   void cyc(long long x) {     swap(a[x + 1], a[x + 2]);     swap(a[x], a[x + 1]);     zs++;     sq[zs] = x;   }   int main() {     long long t, rr, i, j, ii, e;     pair<long long, long long> mne;     scanf( %lld , &t);     for (rr = 0; rr < t; rr++) {       scanf( %lld , &n);       for (i = 1; i <= n; i++) {         scanf( %lld , a + i);       }       zs = 0;       for (i = 1; i <= n - 2; i++) {         mne = {inf, -1};         for (j = i; j <= n; j++) {           mne = min(mne, {a[j], j});         }         e = mne.second;         for (j = e - 2; j >= i; j -= 2) {           cyc(j);         }         if (j == i - 1) {           for (ii = 0; ii < 2; ii++) {             cyc(i);           }         }       }       if (a[n - 1] > a[n]) {         for (i = n - 2; i; i--) {           cyc(i);           if (a[i] <= a[i + 1]) {             break;           }         }         if (!i) {           zs = -1;         }       }       printf( %lld n , zs);       for (i = 1; i <= zs; i++) {         printf( %lld%c , sq[i],    n [i == zs]);       }     }   }   