#include <bits/stdc++.h>
using namespace std;
// macros
typedef long long ll;
typedef long double ld;
typedef pair<int, int> ii;
typedef pair<ll, ll> lll;
typedef tuple<int, int, int> iii;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef vector<iii> viii;
typedef vector<ll> vll;
typedef vector<lll> vlll;
#define REP(a,b,c) for(int a=int(b); a<int(c); a++)
#define RE(a,c) REP(a,0,c)
#define RE1(a,c) REP(a,1,c+1)
#define REI(a,b,c) REP(a,b,c+1)
#define REV(a,b,c) for(int a=int(c-1); a>=int(b); a--)
#define FOR(a,b) for(auto& a : b)
#define all(a) a.begin(), a.end()
#define INF 1e18
#define EPS 1e-9
#define pb push_back
#define popb pop_back
#define fi first
#define se second
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
// input
template<class T> void IN(T& x) {cin >> x;}
template<class H, class... T> void IN(H& h, T&... t) {IN(h); IN(t...); }
// output
template<class T1, class T2> void OUT(const pair<T1,T2>& x);
template<class T> void OUT(const vector<T>& x);
template<class T> void OUT(const T& x) {cout << x;}
template<class H, class... T> void OUT(const H& h, const T&... t) {OUT(h); OUT(t...); }
template<class T1, class T2> void OUT(const pair<T1,T2>& x) {OUT(x.fi,' ',x.se);}
template<class T> void OUT(const vector<T>& x) {RE(i,x.size()) OUT(i==0?"":" ",x[i]);}
template<class... T> void OUTL(const T&... t) {OUT(t..., "\n"); }
template<class H> void OUTLS(const H& h) {OUTL(h); }
template<class H, class... T> void OUTLS(const H& h, const T&... t) {OUT(h,' '); OUTLS(t...); }
// dp
template<class T> bool ckmin(T&a, T&b) { bool bl = a > b; a = min(a,b); return bl;}
template<class T> bool ckmax(T&a, T&b) { bool bl = a < b; a = max(a,b); return bl;}
void program();
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
program();
}
//===================//
// begin program //
//===================//
const int MX = 5e5;
const int N = (1<<20);
int testCases;
int n, a[MX], ra[MX];
void program() {
IN(testCases);
while(testCases--) {
IN(n);
RE1(i,n) IN( a[i]);
RE1(i,n) ra[a[i]] = i;;
// keeping track of the swaps
vii ans;
auto makeSwap = [&](int x, int y) {
swap(a[x],a[y]);
swap(a[n-x+1], a[n-y+1]);
ra[a[x]] = x;
ra[a[y]] = y;
ra[a[n-x+1]] = n-x+1;
ra[a[n-y+1]] = n-y+1;
ans.pb({x,y});
};
RE1(i,n/2) if(ra[i] != i && ra[i] != n-i+1) {
makeSwap(i,ra[i]);
}
vi wrongSide;
RE1(i,n/2) if(a[i] > n/2) wrongSide.pb(i);
// check if it is possible
bool possible = true;
RE1(i,n) if(a[i] + a[n-i+1] != n+1) possible = false;
if(wrongSide.size()%2) possible = false;
if(!possible) {
OUTL(-1);
continue;
}
RE(i,wrongSide.size()) {
makeSwap(wrongSide[i], wrongSide[i+1]);
makeSwap(wrongSide[i], n-wrongSide[i+1]+1);
i++;
}
OUTLS(ans.size(),ans.size());
FOR(p,ans) OUTL(p);
}
}
